In mountainous areas, the earlier melting of snowpacks is depriving trees of needed water supplies during the hot summer months, which further increases their vulnerability to drought. One expert studying these issues, Robert L. Crabtree, told The New York Times recently, "A lot of ecologists like me are starting to think all these agents, like insects and fires, are just the proximate cause, and the real culprit is water stress caused by climate change."

The drought conditions weaken the trees and make them more vulnerable to beetles. And the increasing numbers of forest fires, scientists have long since established, are going up in direct proportion to the rising temperatures. There is no doubt that changes in forest management practices over the last several decades have contributed to the risk, frequency, and size of many forest fires. But the myriad impacts of global warming on fires far exceeds the impact of management practices.

The scale of the losses in the areas being deforested is completely unprecedented, according to experts, and as a result, enormous quant.i.ties of CO2 are being released to the atmosphere. Like the Arctic tundra, the great forests of the world contain large amounts of CO2, in the trees and plants themselves, in the soil beneath them, and in the forest litter that covers it. The great northern boreal forest of Canada and Alaska may have already become a net contributor to CO2 levels in the atmosphere, rather than a net "sink," withdrawing CO2 as the trees grow.

If adequate nutrients are available, the extra CO2 in the atmosphere has the potential to stimulate some additional tree growth, though most experts point out that other limiting factors such as water availability and increased threats from insects and fire are overwhelming this potential. However, in spite of these devastating losses in forestland, the net loss of forests has slowed in recent years, primarily due to the planting of new forests and due to the natural regrowth of trees on abandoned agricultural land. According to the United Nations, most of the regrowth has been in temperate zones, including in forested areas of eastern North America, Europe, the Caucasus, and Central Asia. According to one study, successfully cutting the rate of deforestation in half by 2030 would save the world $3.7 trillion in environmental costs.

China has led the world in new tree planting; in fact, over the last several years, China has planted 40 percent as many trees as the rest of the world put together. Since 1981, all citizens of China older than age eleven (and younger than sixty) have been formally required to plant at least three trees per year. To date, China has planted approximately 100 million acres of new trees. Following China, the countries with the largest net gains in trees include the U.S., India, Vietnam, and Spain. Unfortunately, many of these new forests include only a single tree species, which results in a sharp decline in the biodiversity of animals and plants supported by the monoculture forest, compared to the rich variety supported by a healthy, multispecies primary forest.

For all of the needed attention paid to the sequestration of carbon in trees and vegetation, the amount of carbon sequestered in the first few feet of soil (mainly on the 10.57 percent of the Earth's land surface covered by arable land) is almost twice as much as all the carbon in the vegetation and the atmosphere combined. Indeed, well before the Industrial Revolution and the adoption of coal and oil as the world's princ.i.p.al energy sources, the release of CO2 from plowing and land degradation contributed significantly to the excess of CO2 in the air. By some estimates, approximately 60 percent of the carbon that used to be stored in soils, trees, and other vegetation has been released to the atmosphere by land clearing for agriculture and urbanization since 1800.

Modern industrial agricultural techniques-which rely on plowing, monoculture planting, and heavy use of synthetic nitrogen fertilizers-continue to release CO2 into the atmosphere by depleting the organic carbon contained in healthy soils. The plowing facilitates wind and water erosion of topsoils; the reliance on monocultures, instead of mixed planting and crop rotation, prevents the natural restoration of soil health; and the use of synthetic nitrogen fertilizers has an effect not dissimilar from steroids: they boost the growth of the plants at the expense of the health of the soil and interfere with the normal sequestration of organic carbon in soils.

The diversion of cropland to biofuel plantations also results in a net increase in CO2, while encouraging the destruction of yet more forestland, either directly, as in the case of the peat forests-or indirectly, by pushing subsistence farmers to clear more forests to replace the land they used to plant. As I have previously acknowledged publicly, I made a mistake supporting first generation ethanol programs while serving in the U.S. government, because I believed at the time that the net CO2 reductions would be significant as biofuels replaced petroleum products. The calculations done since then have proven that a.s.sumption to be wrong. I and others also failed to antic.i.p.ate the rapid growth of biofuels and the enormous scale they have now reached worldwide.

THE EXTINCTIONS OF SPECIES.

The destruction of forests-particularly tropical forests that are rich in biodiversity-is also one of the princ.i.p.al factors, alongside global warming, that is driving what most biologists consider the worst consequence of the global environmental crisis: a spasm of extinction that has the potential to cause the loss of 20 to 50 percent of all living species on Earth within this century.

So much heat is already being trapped by global warming pollution that average world temperatures are increasing much more rapidly than the pace to which many animals and plants can adapt. Amphibians appear to be at greatest risk during this early stage, with multiple species of frogs, toads, salamanders, and others going extinct at a rapid rate all over the world. Approximately one third of all amphibian species are at high risk of extinction and 50 percent are declining. Experts have found that in addition to climate change and habitat loss, many amphibians have been hit by a spreading fungal disease, which may also be linked to global warming. Coral species, as noted earlier, are also facing a rapidly increasing risk of extinction.

According to experts, the other factors driving this global extinction event include, in addition to global warming and deforestation, the destruction of other key habitats like wetlands and coral reefs, human-caused toxic pollution, invasive species, and the overexploitation of some species by humans. Many wildlife species in Africa are particularly threatened by poaching and the encroachment of human activities into their territories, particularly the conversion of wild areas into agriculture.

There have been five previous extinction events in the last 450 million years. Although some of them are still not well understood, the most recent, 65 million years ago (when the age of the dinosaurs ended) was caused by a large asteroid crashing into the Earth near Yucatan. Unlike the previous five extinction events, all of which had natural causes, the one today is, in the words of the distinguished biologist E. O. Wilson, "precipitated entirely by man."

Many species of plants and animals are being forced to migrate to higher lat.i.tudes-north in the northern hemisphere and south in the southern hemisphere (one large study found that plants and animals are moving on average 3.8 miles per decade toward the poles)-and to higher alt.i.tudes (at least where there are higher areas to migrate to). One study of a century of animal surveys at Yosemite National Park found that half of the mountain species had moved, on average, more than 500 meters higher.

Some, when they reach the poles and the mountaintops and can go no farther, are being pushed off the planet and into extinction. Others, because they cannot move to new habitats as quickly as the climate is changing, are also being driven toward extinction. A recent Duke University study for the National Science Foundation found that more than half of the tree species in the eastern United States are at risk because they cannot adapt to climate change quickly enough.

Almost 25 percent of all plant species, according to scientists, are facing a rising risk of extinction. Agricultural scientists are especially concerned about the extinction of wild varieties of food crop plants. There are twelve so-called Vavilovian Centers of Diversity, named after Nikolai Vavilov, the great Russian scientist whose colleagues died of starvation during the siege of Leningrad protecting the seeds he had gathered from all over the world. One of them left a letter along with the enormous untouched collection of seeds, saying, "When all the world is in the flames of war, we will keep this collection for the future of the people." Vavilov himself died in prison after his criticism of Trofim Lysenko led to his persecution, arrest, conviction, and death sentence.

The ancient homes of food crops are sources of abundant genetic diversity that serve as treasure troves for geneticists looking for traits that can a.s.sist in the survival and adaptation of food crops to new pests and changing environmental conditions. But many of these have already gone extinct and others are threatened by a variety of factors, including development, monoculture, row cropping, war, and other threats.

The United Nations Convention on Biological Diversity notes, among other examples, that the number of local rice varieties being cultivated in China has declined from 46,000 in the 1950s to only 1,000 a few years ago. Seed banks like the one Vavilov first established are now cataloguing and storing many seed varieties. Norway has taken the lead with a secure storage vault hollowed out of solid rock in Svalbard, north of the Arctic Circle, as a precautionary measure for the future of mankind.

THE LOSS OF living species with whom we share the Earth and the widespread destruction of landscapes and habitats that hundreds of generations have called "home" should, along with the manifold other consequences of the climate crisis, lead all of us to awaken to the moral obligation we have to our own children and grandchildren. Many of those who have recognized the gravity of this crisis have not only made changes in their own lives but have begun to urge their governments to make the big policy changes that are essential to securing the human future.

THE PATH FORWARD.

Generally speaking, there are four groups of policy options that can be used to drive solutions to the climate crisis. First and most important, we should use tax policy to discourage CO2 emissions and drive the speedier adoption of alternative technologies. Most experts consider a large and steadily rising CO2 tax to be the most effective way to use market forces to drive a large-scale shift toward a low-carbon economy.

Economists have long understood that taxes do more than raise revenue for the governments that impose them; to some extent, at least, they also discourage and reduce the economic activities that are taxed. By using taxes to adjust the overall level of cost attributed to the production of CO2 and other greenhouse gases, governments can send a powerful signal to the market that, in the best case, unleashes the creativity of entrepreneurs and CEOs in searching for the most cost-effective ways of reducing global warming pollution. That is the reason I have advocated the use of CO2 taxes for thirty-five years as the policy most likely to be successful. And implementing the tax in a way that escalates over time would provide the long-term signal to industry and the public that is needed to plan effective changes over coming decades.

Taxes, of course, are always and everywhere unpopular with those who pay them. Therefore, the enactment of this policy requires strong and determined leadership and, to the extent possible, bipartisanship. In recognition of those simple but significant political facts of life, I have always recommended that CO2 taxes be coupled with reductions in other taxes by an equal amount.

Unfortunately, most people are far more willing to believe that government will indeed impose a new tax, but far less willing to believe that it will give that revenue back in another form. The forty-year campaign in the U.S. by the conservative counterreform alliance led by corporate interests and business elites has been effective in demonizing government at all levels and pursuing a "starve the beast" strategy that focuses on shrill opposition to any tax of any kind-unless the tax in question falls on low-income wage earners.

Other versions of this proposal have coupled the CO2 tax with a rebate plan, to send a check to each taxpayer. Under this approach, sometimes labeled the "fee and dividend" approach or "feebate," those who were more successful in reducing their CO2 emissions would actually make money, or use it to pay for more efficient or renewable energy technologies. Yet another version, which was introduced in the U.S. Congress in 2012 but never voted upon, would return two thirds of the revenue raised by a carbon tax to the taxpayers but would have applied one third to a reduction in the budget deficit. Unfortunately, the ingrained opposition to any new taxes-even if they are revenue neutral-has thus far made it difficult to build support for the single most effective strategy for solving the climate crisis, a CO2 tax.

A second set of policy options involves the use of subsidies. To begin with, we should immediately remove existing subsidies that encourage fossil fuel consumption. In the United States, for example, approximately $4 billion each year-mainly in the form of special tax subsidies-go to carbon fuel companies. In India, to pick another example, the dirtiest liquid fuel, kerosene, is heavily subsidized.

Instead, governments should provide robust subsidies for the development of renewable energy technologies, at least until they reach the scale of production that will bring sufficient cost reductions to enable them to be compet.i.tive with unsubsidized fossil fuels. This policy would be even more effective in combination with a CO2 tax, which would appropriately include in the price of fossil fuels some of the enormous costs they impose on society.

Limited government subsidies have already been successful in promoting more rapid adoption of renewable energy technologies. In fact, the cost reductions a.s.sociated with the increasing scale of production have now put some renewable technologies much closer to a price that makes them compet.i.tive with coal and oil. Both solar and wind technologies are only a few years away from reaching that threshold. Yet the large carbon polluters and their allies have been working hard to eliminate subsidies for renewable energy before these clean technologies can become compet.i.tive with dirty energy-which is ironic, given that the global subsidies for the burning of fossil fuels, described above, greatly exceed the subsidies for renewable sources of energy, even though the latter are often miscalculated and misstated by opponents, who lump them in with subsidies for nuclear energy, so-called clean coal technologies, and other nonrenewable options.

The third policy option is an indirect subsidy for renewable energy in the form of a mandate requiring utilities to achieve a certain percentage of electricity production from renewable sources. This mechanism has already worked in numerous nations and regions, though many in the utility sector oppose such measures. Several U.S. states-including, most prominently, California-have successfully implemented this approach, and it is a major factor in the increased renewable energy installations in the United States. Germany has been perhaps the most successful nation in the world in using this policy option to stimulate the rapid adoption of both solar and wind technologies.

On a global basis, the combination of government subsidies for the speedier development of renewable energy technologies and the requirements that some utilities use them to produce a higher percentage of the electricity they generate has contributed to dramatic advances far beyond what most predicted. In 2002, a leading energy consulting firm projected that one gigawatt of solar electricity would be produced worldwide by 2010; that goal has been exceeded by seventeen times. The World Bank projected in 1996 that China would install 500 megawatts of solar energy by 2020. China installed double that amount by 2010.

The past projections of increased wind energy have also turned out to be overly pessimistic. The U.S. Department of Energy projected in 1999 that the U.S. wind capacity would reach ten gigawatts by 2010. Instead, that goal was met in 2006 and has now been exceeded four times over. In 2000, the U.S. Energy Information Agency projected that worldwide wind capacity would reach thirty gigawatts by 2010. Instead, that goal was exceeded by a factor of seven. The same agency projected that China would install two gigawatts of wind by 2010; that goal was exceeded 22-fold and is expected to be exceeded 75-fold by 2020.

As Dave Roberts of the environmental magazine Grist has pointed out, the world has previously witnessed predictions for the adoption of new technology that "weren't just off, they were way off." Industry and investor predictions at the beginning of the mobile telephone revolution, for example, wildly underestimated how quickly that new technology would spread. After the Arab-OPEC oil embargos in the 1970s, projections for the adoption of energy efficiency measures were also way off. What both of these prior examples have in common with renewable energy technologies is that all three are "widely dispersed" technologies that experienced unpredicted exponential growth because of a virtuous cycle, within which the increasing scale of production drove sharply lower costs-which in turn drove even faster growth.

The most frequently cited precedent for this phenomenon is the computer chip industry. As noted earlier, Moore's Law-which accurately predicted the relentless 50 percent cost reduction for computer chips every eighteen to twenty-four months-is not a law of nature, but instead a law of investment. In the early days of the computer revolution sixty years ago, chip manufacturers came to two conclusions: first, the potential market for computer chips was enormous and fast-growing-almost limitless; second, the technology development path was highly sensitive to innovation.

These dual realizations caused the leading chip manufacturers to devote enormous sums to research and development in order to protect their prospective market share against compet.i.tors. Over time, a collective consensus emerged that so long as they could continue reducing their costs on the pathway described by Moore's Law, they would be likely to retain or grow their market share. In other words, Moore's Law was transformed from a description of the past into a self-fulfilling prophecy about the future. Policies designed to create the rational expectation of steadily growing markets for renewable energy technologies can steepen a similar self-sustaining cost reduction curve for renewable energy.

The fourth policy option is widely known as cap and trade. This proposal is also designed to mobilize market forces as an ally in achieving CO2 reductions. In spite of the relentless attacks on the mechanism, cap and trade remains favored by many policy experts as the best approach for securing a global agreement. Although I strongly favor a CO2 tax, one of its disadvantages is that it is difficult to imagine coordinating national tax policies in many countries around the world with widely differing tax systems and differing compliance records. By contrast, a global cap and trade system would be inherently easier to harmonize among countries around the world with widely varying tax systems.

Cap and trade is based on an extremely successful policy innovated by former president George H. W. Bush to reduce emissions of sulfur dioxide (SO2) in order to mitigate the acid precipitation in states downwind to the north and east of the Midwestern coal plants. The policy was embraced by Republicans as an alternative to government regulations mandating reductions in each plant.

The theory was that a slowly declining limit on emissions, when coupled with an ability to buy and sell emission "permits," would maximize reductions by giving a market incentive to those companies that were most efficient in limiting emissions, while simultaneously allowing a little more time for those companies having difficulty. The results were astoundingly successful. Emissions dropped much faster than predicted at a cost that was only a fraction of what was predicted. Consequently, advocates of CO2 reductions felt that this mechanism could serve as a bipartisan compromise that would effectively reduce global warming pollution.

Unfortunately, as soon as cap and trade was presented as a bipartisan compromise, many conservatives who had originally supported the idea turned against it and began calling it "cap and tax." Thus have fossil fuel companies and their ideological allies paralyzed the policymaking process both at the global level and in the United States.

For many years, the effort to achieve a global consensus on action to solve the climate crisis was bedeviled by the international fault line between rich and poor nations, with poor countries insisting that the priority they placed on quickly replicating the economic development that had already occurred in wealthy countries meant that they could not afford to partic.i.p.ate in a global effort to reduce global warming pollution. Proposed treaties routinely placed the first obligations on wealthy countries alone, leaving any requirements on developing nations to future rounds of negotiation.

After all, the need for more energy to power sustainable economic development in poor countries is acute. An estimated 1.3 billion people in the world still have no access whatsoever to electricity, and in spite of historic reductions in global poverty, the per capita income levels in many energy-poor countries are so low that it is easy to understand why they have resisted any constraints on potential increases in CO2 emissions at a time when the wealthier countries have made such profligate use of fossil energy during their own past periods of economic takeoff and development.

Much has changed, however. The reality of the climate crisis has become much more apparent in developing nations as they experience harsh impacts and struggle to find the resources for disaster recovery and adaptation that are more readily available in developed countries. As a result, many developing countries have now changed their tune and are actively pushing the world community to take action on climate, even if it means that they too must shoulder part of the burden for responding. The World Bank estimates that more than three quarters of the costs from climate disruption will be borne by developing countries, most of which lack the resources and capacities to respond on their own.

Expenditures for the installation of renewable energy sources in the developing world now exceed those in rich countries. According to David Wheeler at the Center for Global Development, developing countries now are responsible for two thirds of the new renewable energy capacity since 2002 in the world, and overall have more than half of the installed global renewable energy capacity.

Even the richest countries are now being forced to recognize the economic toll of climate-related disasters. In the U.S.-still the richest country in the world-political controversies over the rising costs of disaster relief have resulted in cutbacks to emergency recovery programs that have hampered the ability of many communities to get back on their feet after climate calamities. But 201112 was a wakeup call.

In 2011, the U.S. had eight climate-related disasters, each costing over $1 billion. Tropical Storm Irene, which mostly missed New York City, nevertheless caused more than $15 billion in damage. Texas experienced the worst drought and highest temperatures in its history, and wildfires in 240 of its 242 counties. Thousands of daily all-time-high temperature records were broken or tied. Tornadoes, which climate researchers are still unwilling to link to global warming (partly because the records of past tornadoes are incomplete and imprecise), ravaged Tuscaloosa, Alabama, Joplin, Missouri, and many other communities; seven of them caused more than $1 billion in damage. In 2012, more than half of the counties in the U.S. suffered from drought. Hurricane Sandy cost at least $71 billion.

One of the princ.i.p.al objections to cap and trade in the United States has been based on the fear that developing countries would not be subject to the proposal and that U.S. industries would therefore be at a compet.i.tive disadvantage. In the last two decades, the emergence of Earth Inc. has inspired fear among factory workers in the U.S. and other developed nations that their jobs were being taken away and redistributed to factory workers in poorer countries where labor was cheap and advanced technologies were becoming available. Consequently, any perceived additional compet.i.tive advantage for developing countries became politically toxic in much of the industrial world.

That is one of many reasons why there is support for proposals to integrate CO2 reductions into the World Trade Organization's definition of what is permitted by way of "border adjustments" to add the cost of CO2 reductions to the price of imported goods from a country that does not require them to a country that does. In 2009, the World Trade Organization and the United Nations Environment Programme jointly published a report supporting such border adjustments.

I have long been a vocal advocate of reciprocal free trade even though that position did not endear me to my own political party. And I continue to strongly believe in free and fair international trade. But a fair set of rules is one that is designed to create and maintain a level playing field, and, in my view, CO2 reductions certainly qualify as one of the factors that should be included in border adjustments.

When I was vice president, I joined with others in negotiating a global treaty in Kyoto, j.a.pan, to adopt the cap and trade mechanism as the basis for the world's effort to reduce CO2 emissions. The Kyoto Protocol was adopted by 191 countries and by the European Union as a whole, and in spite of the U.S. refusal to partic.i.p.ate, and in spite of implementation problems, has been a success in most of the nations, provinces, and regions that are striving to meet its commitments.

Even though some nations using carbon credit trading have manipulated and abused the system, and even though problems emerged in the early days of the European system, Europe has taken action to address the problems and most nations with well-designed systems are on course to sharp emissions reductions. One policy a.n.a.lyst with the Potsdam Inst.i.tute for Climate Impact Research, Bill Hare, said, "I can't see any other way to do it. Other policies are not easier to negotiate. The carbon market may be complex, but we live in a complex world."

Unfortunately, the decision by the United States not to join the Kyoto Protocol and the failure to gain commitments from China and other "developing countries" (China in those years was still labeled a developing country) meant that the two largest emitters of global warming pollution were not included. If the U.S. had joined, the momentum for global partic.i.p.ation and compliance would have been overwhelming and developing countries would have faced unrelenting pressure to join in the treaty's second phase, as antic.i.p.ated.

Yet even though the U.S. political system is still paralyzed at the federal level, governments of many other nations are beginning to adopt new policies in recognition of the dangers we face and the opportunities to be seized. In addition to the European Union, Switzerland, New Zealand, j.a.pan, one Canadian province, and twenty U.S. states will imminently begin cap and trade systems. Most significantly, California began implementing its system in 2012.

Australia, the largest coal exporter in the world, has adopted a plan that includes both a CO2 tax and a cap and trade system that has been linked to the European Union's system. South Korea is in the process of setting up its own system and fourteen other countries have announced formally that they are planning to launch cap and trade systems: Brazil, Chile, Colombia, Costa Rica, India, Indonesia, Jordan, Mexico, Morocco, South Africa, Thailand, Turkey, Ukraine, and Vietnam.

Wolfgang Sterk of the Wuppertal Inst.i.tute in Germany says, "The carbon market is not dead.... If a national system emerges in China, depending on the design and scope, it may become the biggest in the world, and allowances in that system would then give a global price signal."

China is implementing a cap and trade system in five cities (Beijing, Tianjin, Shanghai, Chongqing, and Shenzhen) and two provinces (Guangdong and Hubei). These pilots are intended to be up and running in 2013 in order to provide a learning experience that will be used to implement a nationwide cap and trade system by 2015.

As with some of the other commitments made by the Chinese government, some experts remain skeptical that they will follow through on this plan, but observers report that progress has already been made in most of the pilots that were designated. Together, the areas in the pilot program represent almost 20 percent of the Chinese population and almost 30 percent of its economic output.

China's commitment to sustainability and renewable energy has at once helped and hurt the world's ability to solve the climate crisis. By limiting imports while using subsidies to drive the cost of renewable energy technologies below the level at which Western companies can compete, China has served its own interest in dominating what everyone expects to be a key industry of the twenty-first century, but has damaged the rest of the world's ability to reap the benefits of fair compet.i.tion in quickly advancing the state of these technologies.

In 2011, the United States filed a formal complaint against China for allegedly providing unfair subsidies to its wind and solar manufacturers. As of 2012, the U.S. imposed tariffs of approximately 30 percent on Chinese-imported solar panels, and the European Union began its consideration of a similar complaint. Nevertheless, in spite of these problems, the low prices that resulted from China's commitment and subsidies helped drive the scale of production to higher levels than anyone predicted, thus producing sharper cost reductions than antic.i.p.ated.

China's impressive commitment to move forward aggressively with the deployment of wind and solar has inspired many other nations around the world, but its continuing enormous investment in new coal-fired generating plants has caused it to overtake the United States as the largest global warming polluter on the planet. Everyone realizes the importance to China of continuing its development of business and industry in order to continue reducing the levels of abject poverty in its country, but protests inside China against dirty energy projects are growing in several regions.

In the last ten years, China's energy consumption has gone up more than 150 percent, surpa.s.sing that of the U.S. And, unlike the United States, China still gets approximately 70 percent of its energy from coal. Its coal consumption has increased 200 percent over the same decade, to a level three times that of U.S. coal consumption. China is both the largest importer of coal in the world (followed by j.a.pan, South Korea, and India) and the largest producer of coal, by far-producing half of the world's coal, two and a half times more than the U.S. (which is the second-largest producer of coal). Indeed, the amount by which China's coal consumption increased from 2007 to 2012 amounts to additional demand that is equivalent to all of the U.S. annual consumption. Beijing has proposed a cap on coal production and use to be implemented in 2015, though many experts are skeptical about their ability to stay within the cap.

Even though its appet.i.te for oil pales in comparison to its consumption of coal, the amount of oil China used doubled during the 1990s, doubled again in the first decade of this century, and is now second only to that of the United States. For the first time, in 2010, Saudi Arabia's oil exports to China exceeded those to the U.S. In 2012, China's domestic oil reserves appeared to have peaked. And even though they are aggressively developing offsh.o.r.e oilfields, the Chinese already import half the oil they use, and the U.S. Energy Information Agency predicts that China will import three quarters of its oil within the next two decades.

Security experts have noted that this trend has implications for Chinese foreign policy in areas like the disputed reserves in the South China Sea and its forward-leaning engagement with oil-rich countries in the Middle East and Africa. Many observers found it ironic that after the United States invaded Iraq-at least in part to ensure the security of Persian Gulf oil supplies-the Chinese became the largest investor in Iraq's oilfields.

On a per capita basis, energy consumption in China is only a fraction of that in the U.S. and other more developed countries, though its per capita CO2 emissions are approaching those of Europe. Since the reforms of Deng Xiaoping were implemented more than thirty years ago, China has converted much of its economy from agriculture to industry and the transition has been even more energy-intensive because of subsidies to fossil fuels-which reduce energy efficiency in every country that uses them. In fact, electricity rates, petroleum product prices, and natural gas prices are all fixed by the government at below market levels, though there is active debate in Beijing about letting all energy prices float further upward to global market levels. Overall, China is lagging behind other leading global economies in crucial areas of energy efficiency.

In spite of its energy challenges and its ma.s.sive CO2 emissions, China has implemented an extremely impressive set of policies to stimulate the production and use of renewable energy technologies. In its latest Five Year Plan, China announced that it will invest almost $500 billion in clean energy. The Chinese make use of "feed-in tariffs," a complex subsidy plan that worked extremely well in Germany. China also uses a full range of other policies, including tax subsidies and the imposition of renewable energy percentage targets on utilities.

In addition to capping the use of coal, it has also established a number of hard targets for the reduction of CO2 emissions per unit of economic growth. A former vice minister of environmental protection, Pan Yue, said in 2005 that China's economic "miracle will end soon, because the environment can no longer keep pace."

In the last decade, there has been tension between goals set by the national government and implementation strategies pursued by regional governments, which are typically intertwined with industrial energy users. As a measure of the national government's seriousness in enforcing the CO2 reduction and energy intensity reduction targets, Beijing sent officials to these regions in 2011 to impose forced closings of factories and even blackouts in order to ensure that the goals were met. More recently, the central government has linked promotions of local and regional officials to their success in achieving these goals.

In the renewable energy sector, China has dominated global production of windmills and solar panels, as noted above, but has made less progress in the installation of solar panels than it has in installing windmills-partly because it exports 95 percent of the solar panels it produces, many of them to the United States. In some recent years, 50 percent of all the windmills installed globally were in China, though almost a third of its windmills either are not connected to the electricity grid or are connected to lines that cannot handle the electricity flow.

The central government is also directing an ambitious plan to build the most sophisticated and extensive "super grid" in the world in order to remedy this problem. Beijing has announced that it will spend $269 billion over the next few years on construction of 200,000 kilometers of high-voltage transmission lines, which one industry trade publication noted is "almost the equivalent of rebuilding the United States' 257,500-kilometer transmission network from scratch."

As many countries have realized, high-capacity, high-efficiency electricity grids are essential in order to use intermittent sources of electricity like those produced by windmills and solar panels, and to transmit renewable electricity from the areas of highest potential production to the cities where it is used. As the percentage of electricity from the sources increases, the importance of smart grids and super grids will increase.

Plans are proceeding to link the high-sun areas of North Africa and the Middle East to large electricity consumers in Europe. Similar plans are on the drawing boards in North America, where high-sun areas of the Southwestern U.S. and northern Mexico can easily provide all of the electricity needed in both countries. And in both India and Australia, plans are under way to link high-sun and -wind regions with high-electricity-consuming regions.

There is, in any case, a powerful need to upgrade the reliability, carrying capacity, and advanced features of the electricity distribution grid in rich and poor countries alike. In the U.S., for example, interruptions in electrical service and unplanned blackouts, combined with inefficiencies in distribution and transmission, impose an estimated annual cost of more than $200 billion per year. In India, the largest blackout in history-by far-occurred in 2012 when more than 600 million people lost power due to problems in managing electricity flows through the antiquated grid system.

In addition to the development of super grids and smart grids-which can empower end-users of electricity with tools to become far more efficient in their ability to reduce energy consumption and save money-there is a pressing need for more efficient ways to store energy. A great deal of investment has gone into the research and development of new batteries that can be distributed throughout the electrical grid and in homes and businesses in order to reduce the need for wasteful overcapacity in electrical generation that is needed during the peak hours of use. These batteries can also provide valuable electricity storage when used in electric cars that, like most cars, spend the vast majority of their time in garages or parking s.p.a.ces.

Toward that end, automakers around the world are launching fleets of electric vehicles in antic.i.p.ation of a shift toward renewable electricity and away from expensive and risky petroleum supplies. At least some manufacturers in almost every industry are also converting to strategies that emphasize lower energy and material consumption. Energy efficiency expert Amory Lovins, of the Rocky Mountain Inst.i.tute, has thoroughly doc.u.mented the impressive movement by many companies to take advantage of these opportunities.

In addition to solar and wind, wave and tidal energy are both being explored-in Portugal, Scotland, and the United States, for example-and although the contribution from these sources is still minuscule, many believe that they may have great potential in the future. Nevertheless, the Intergovernmental Panel on Climate Change, in a special report on renewable energy sources in 2011, said that wave and tidal power are "unlikely to significantly contribute to global energy supply before 2020."

Geothermal energy has made a significant contribution in nations like Iceland, New Zealand, and the Philippines, where there is an abundance of easily exploitable geothermal energy. The vast potential for geothermal energy derived from much deeper geological regions has been unexpectedly difficult to develop, but here again, entrepreneurs in many countries are working hard to perfect this technology.

Although the potential for hydroelectric energy has been almost fully exploited in major areas of the world, there are undeveloped resources in Russia, Central Asia, and Africa that have great potential, though critics also warn about serious ecological risks in particular locations.

The use of bioma.s.s is expanding, and in some countries is beginning to play a significant role. In addition to traditional uses of manure and other forms of bioma.s.s for cooking, modern bioma.s.s techniques are being used to burn wood from renewable forests in far more efficient processes to produce heat and electricity. As with biofuels, the net impact of bioma.s.s use, when a.n.a.lyzed on a lifecycle basis, depends a great deal on the careful calculation of all of the energy inputs, the impact on land use and biodiversity, and the time periods required to recycle the carbon through the regrowth of the plants and trees.

There is also a global movement to produce methane and syngas from landfills containing large amounts of organic waste, and to produce biogas from large concentrations of animal waste gathered in animal feedlot operations. China, for example, has a major focus on biogas-requiring the installation of biogas digesters at all large cattle, pig, and chicken farms to derive the gas from animal waste, though enforcement of this mandate has been lagging. The U.S., which has a voluntary program, and other countries should follow their lead.

FALSE SOLUTIONS.

There are two strategies for responding to global warming that are unlikely to work, even though each one has enthusiastic supporters. The first is carbon capture and sequestration (CCS). I have long supported research and development of CCS technologies, but have been skeptical that they will play more than a minor role. It is always possible that there will be an unexpected technological breakthrough that greatly reduces the cost of capturing CO2 emissions and either storing them safely underground or transforming them in some manner into building materials or other forms that make them useful and safe. My friend Richard Branson has established a generous prize for the removal of CO2 from the atmosphere, and invited NASA scientist and global warming expert Jim Hansen and me to be judges in the compet.i.tion.

Barring breakthroughs, however, the cost of the CCS technology presently available-both in money and energy-is so high that utilities and others are unlikely to use it. A utility operating a coal-fired generating plant and selling electricity to its customers would have to divert approximately 35 percent of all the electricity it produces just to provide power for the capture, compression, and storage of the CO2 that would otherwise be released into the atmosphere. While that might be interpreted as a bargain if it saved civilization's future, the utility could not afford to do it and still stay in business. And the volumes of CO2 emissions involved are so enormous that taxpayers do not have much appet.i.te for shouldering the expense.

While safe and secure underground storage areas do exist, the process of locating them and then painstakingly investigating their characteristics in order to ensure that the CO2 will not leak to the surface and into the air is quite significant. There has been notable public opposition to the siting of such underground storage facilities near populated areas. The consensus among those scientists and engineers who are experts in this subject is that the longer the CO2 is stored, the safer it becomes-because it begins to be absorbed into the geological formation itself. Nevertheless, the overall expense of CCS has prevented its adoption by large carbon polluters.

Both the United States and China announced large government-financed demonstration projects for CCS, though the Chinese project-known as GreenGen-is behind schedule, and the U.S. project-called FutureGen-is mired in the endemic political paralysis that characterizes the present state of democracy in the United States. Norway, the United Kingdom, Canada, and Australia are among the other countries pursuing CCS. However, one of the world's leading experts on CCS, Howard Herzog of the Ma.s.sachusetts Inst.i.tute of Technology, has said for years that the real key to making this technology profitable and viable is to put a price on carbon.

The second technology that is sometimes described as a silver bullet that could eliminate most CO2 emissions, at least from the electricity-generating sector, is one with a long and fraught history-nuclear power. The present generation of 800 to 1,200 megawatt pressurized light water reactors is, unfortunately, probably a technological dead end. For a variety of reasons, the cost of reactors has been increasing significantly and steadily for decades. In the aftermath of the triple tragedy in f.u.kushima, j.a.pan, the prospects for nuclear energy have further declined.

The safety record, while much improved, is still one that has been producing public opposition. France, which used to have a global reputation as the most advanced and efficient nation in nuclear power, has had difficulties with its new generation of reactors. South Korea, on the other hand, has been moving forward with a design that many experts believe is promising. Several new reactors are under construction around the world, but as our low-carbon energy options are evaluated, nuclear energy is severely hampered by both cost and perceived safety issues. There is still a distinct possibility that the research and development of a new generation of smaller and hopefully safer reactors may yet play a significant role in the world's energy future. We should know by 2030.

In spite of their problems, both CCS and nuclear power have had enduring appeal, partly because they are technological solutions that offer the possibility that a single strategy might lead to a relatively quick fix. Indeed, psychologists tell us that one of the other glitches in our common way of thinking about big problems is what they call "single-action bias," a deeply ingrained preference for single solutions to problems, however complex the problems may be.

This same common flaw in our way of thinking helps to explain the otherwise inexplicable support for a number of completely bizarre proposals that are collectively known as geoengineering. Some engineers and scientists argued several years ago that we should float billions of tiny strips of tinfoil in orbit around the Earth to reflect more incoming sunlight and thereby cool down the global temperature. The public record does not indicate whether they were wearing tinfoil hats when they launched their idea. An earlier proposal in the same vein featured a giant s.p.a.ce parasol, also intended to block incoming sunlight. It would have had to be 1,000 miles in diameter and would have required a moon base for its construction and launch. Others have suggested that we attempt to accomplish the same result by injecting ma.s.sive quant.i.ties of sulfur dioxide into the upper atmosphere in order to block sunlight.

The fact that any reputable scientist would lend his or her name to such proposals is certainly a measure of the desperation that those who understand the climate crisis feel about the abject failure of the world's political leadership to begin reducing the rate of emissions of global warming pollution. But given the unantic.i.p.ated consequences of the planetary experiment we already have under way-pumping 90 million tons of heat-trapping pollution into the atmosphere every twenty-four hours-it would, in my opinion, be utterly insane to launch a second planetary experiment in the faint hope that it might temporarily cancel out some of the consequences of the first experiment without doing even more harm in the process.

Among the other consequences of the SO2 proposal that was pointed out in a 2012 scientific study is this startling change: the sky we have gazed at since the beginning of humankind's existence on Earth would no longer be blue-or at least no longer be as blue. Does that matter? Perhaps we could explain to our grandchildren why there were so many references to "blue skies" in the history of the cultures on Earth. Maybe they would understand that it was necessary to sacrifice the blueness of the sky in order to accommodate the political agenda of oil, coal, and gas companies. The levels of pollution above cities have already changed the color of the night sky from black to reddish black.

No one has any idea what such proposals would mean for the photosynthesis of food crops and other plants; light needed for life would be partially blocked in order to create more "thermal s.p.a.ce" to be occupied by steadily increasing emissions from the burning of fossil fuels. The effectiveness of photovoltaic conversion of sunlight into electricity-one of the most promising renewable energy technologies-might also be damaged. And none of these exotic proposals would do anything whatsoever to halt the acidification of the oceans.

In addition, if we failed to reduce CO2 emissions, the sulfur dioxide injections or orbiting tinfoil strips would have to be increased steadily, year by year. Nor does anyone have the faintest idea of what these wack-adoodle proposals would do to climate patterns, precipitation, storm tracks, and all of the other phenomena that are already being disrupted. Have we gone stark raving mad?

No, we haven't gone mad. It's just that our way of communicating about global challenges and debating reasonable solutions has been subjected to an unhealthy degree of distortion and control by wealthy corporate interests who are themselves desperate to prevent serious consideration of reducing global warming pollution.

Technically, there are a range of benign geoengineering proposals that may well offer marginal benefits without imposing reckless risks. Painting roofs white, for example, or planting millions of roof gardens are both examples of riskless changes to the reflective characteristics of the Earth's surface that could bounce more of the incoming sunlight back into s.p.a.ce before the heat energy it carries is absorbed in the lower atmosphere. In a variation on this theme, Peru is painting rocks white high in the Andes in a desperate effort to slow the melting of glaciers and snowpacks on which they rely for drinking water and irrigation.

If we continue to delay the launching of a serious multip.r.o.nged global effort to reduce the emissions of heat-trapping greenhouse gas pollution, we will find ourselves pushed toward increasingly desperate measures to mitigate the growing impacts of global warming. We will try to muddle through, argue and fight with one another, pursue our self-interest at the expense of others, often deceiving them and ourselves in the process. That is the course that we are on now.

But when the survival of what we hold most dear is clearly at risk, then we must act. In all of human history, there have been rare moments when we have risen to transcend our past and charted a new course to safeguard our deepest values. At one such challenging moment in history, Abraham Lincoln said, "The occasion is piled high with difficulty, and we must rise with the occasion. As our case is new, so we must think anew, and act anew. We must disenthrall ourselves, and then we shall save our country."

This time, our world is at stake. Not the planet itself; it would, of course, survive nicely without human civilization, albeit in an altered state. Rather, what is at stake is the set of environmental conditions and the health of the natural systems on which our civilization depends. And the fact that this crisis is global in nature is part of the unique challenge we face.

Only twice before in all of human history has the future of our entire global civilization been at risk. Once, at the dawn of h.o.m.o sapiens' time on Earth 100,000 years ago, anthropologists tell us that our numbers were reduced to less than 10,000 people, yet somehow we prevailed. The second occasion was when the United States and the former Soviet Union came all too close to unleashing ma.s.sive nuclear a.r.s.enals against one another, killing hundreds of millions and risking a nuclear winter with potentially apocalyptic consequences. And again, somehow we prevailed.

This time, the threat to our future is one that would not arrive in a matter of minutes with bright flashes and deafening sounds. It would be drawn out, and generations yet to come would live all their lives with the painful knowledge that once upon a time the Earth was hospitable to humans. It sustained and nourished us with cool breezes and abundant food and water. It inspired and renewed us with its majestic beauty.

When memories of that Earth faded, the story would still be told: in the early decades of the twenty-first century, a generation gifted by those that came before them with the greatest prosperity and most advanced technologies the Earth had ever known broke faith with the future. They thought of themselves and enjoyed the bounty they had received, but cared not for what came after them. Would they forgive us? Or would they curse us with the dying breaths of each generation to come?

If, on the other hand, we do find a way to rise to this occasion, we will have the rare privilege of meeting and overcoming a challenge that is worthy of the best in us. We have the tools we need. Some of them, it is true, need repair. Others need to be improved and perfected for the task ahead. All that we lack is the will to prevail, but political will can be renewed and strengthened by acknowledging the truth of our circ.u.mstances and accepting our obligation to safeguard the future for the next generation and all who will follow them.

What we most need is a shift in our way of thinking and a rejection of the toxic illusions that have been so a.s.siduously promoted and continually reinforced by opponents of actions, princ.i.p.ally large carbon polluters and their allies. In some ways, this struggle to save the future will be played out in a contest between Earth Inc. and the Global Mind. The interconnection of people all over the world by means of the Internet has created the potential for an unprecedented global effort to communicate clearly among ourselves about the challenge that now confronts us and the solutions that are now available.