American global warming

Imagine if the world's two largest polluters unilaterally decide to cut emissions of carbon dioxide, the ubiquitous gas responsible for the bulk of global warming. At the same time, a major developing country admits that future growth will have to be balanced with CO2 pollution limits. Meanwhile, an industrialized nation country takes responsibility for the layer of greenhouse gases it has already added to the atmosphere.

Even better, alternatives to burning fossil fuels to generate electricity or propel vehicles get cheap and begin to be deployed at significant scale. The clearing and cutting of the world's forests slows. Even farmers who don't particularly believe in climate change begin to take steps to restore carbon to depleted soils to boost fertility.

That's what significant action to combat climate change would look like. And that's exactly what is happening in the world right now.

No matter what comes out of the traveling circus known as the Conference of the Parties to the United Nations Framework Convention on Climate Change in Lima, Peru over the next few weeks, nations are taking action to curb global warming on their own. And by the end of the meeting in Lima, the world should be well on its way to delivering national commitments for combating climate change.

Of course, it's not all good news. Japan's pollution has risen anew thanks to the shutdown of nuclear reactors in the wake of the Fukushima meltdowns. Canada has repudiated its commitments under the Kyoto Protocol and seems content to let pollution rise as much and as fast as possible, perhaps because a warmer Arctic might let it find yet more tar sands and other natural resources (not unlike seemingly pro-global warming Russia). And Australia has seen its pollution swell with the repeal of its carbon tax.

Decades of delay mean hopes of restraining global warming to less than 2 degrees Celsius or limiting CO2 concentrations in the atmosphere to less than 450 parts-per-million may seem a little unrealistic. In fact, if the world can only add roughly 1 trillion metric tons of carbon to the atmosphere as has been suggested by scientists, then half has already been burned and the rest could go up in smoke in the next few decades. The world still gets 80 percent of all its energy from burning fossil fuels. No wonder geoengineering—the deliberate manipulation of the planet's climate by sucking CO2 back out of the air or blocking sunlight—has begun to be suggested as a backup plan.

Yet, there is still hope. The world's biggest polluter—China—will attempt to reach a peak in its voluminous output of greenhouse gases by 2030 under the terms of a new agreement with the U.S., and not a peak that is the size of the Himalayas on its borders. Under that same agreement, the U.S. will attempt to cut its CO2 pollution by as much as 28 percent by 2025. The European Union rounds out the world's biggest industrial polluters by committing to a 40 percent cut by 2030.

• Humans global warming
• Trends in global warming
• Help stop global warming