How do we do something about the trends in global warming?


It is too late to stop global warming, but we can limit its rise. From 1900 to 2005, says the Intergovernmental Panel on Climate Change, or IPCC, the planet’s average surface temperature rose about .72ºC (1.3ºF) — and greenhouse gases, particularly CO2, are very likely the explanation.

The IPCC report goes on to say that if people continue to force CO2 to build up in the atmosphere by burning fossil fuels, cutting down forests and other activities, the planet will continue to warm.

Even if we could somehow keep emissions from growing, we would still be pumping greenhouse gases into the atmosphere at a higher rate than any time in history — roughly 30 billion metric tons of CO2 per year from fossil fuels, in addition to some non-CO2 greenhouse gases. These gases would continue to build up in the atmosphere. That’s because natural processes remove greenhouse gases from the atmosphere more slowly than we currently add them.

But what if we could stop CO2 emissions completely instead of just keeping them from growing? Even then, the warming triggered by the gases we have already emitted could last for more than a thousand years. We would not return to the temperatures and sea levels we have been accustomed to until after the year 3000.

So, the question is not how we stop warming, but rather how we limit it. There is a consensus among scientists that if the global average temperature rises 2ºC (3.6ºF) above the preindustrial temperature, there will be serious climate impacts. To stay under that limit, while allowing for economic growth in less-developed countries, industrialized countries like the US would have to cut their carbon emissions some 80 percent by the year 2050, compared with 2005 levels, according to one commonly cited calculation. The world as a whole would have to cut carbon emissions by 50 percent overall. Some of that could come from using energy more efficiently — by using better home insulation, more efficient appliances, and cars that get much better gas mileage. That could get us large reductions, but not 80 percent.

To get that much, we would have to change the way energy is produced.

Currently, the US gets 85 percent of its energy from
CO2-emitting coal, oil, and natural gas and 15 percent from non-fossil sources like nuclear or renewables. We would need to reverse this equation. There is enough nuclear, wind, solar, hydroelectric, “clean coal” — where CO2 is captured and stored underground — and other non-emitting energy to do this, especially if efficiency can reduce our total energy needs substantially. This, however, would require a huge change in our energy system — and it probably could not be done without higher costs for energy.

The only reason to spend a lot on fighting climate change would be if we think the cost of inaction would likely be even greater — and many economists believe just that. According to the Stern Review, a highly regarded analysis issued in 2006, doing nothing to reduce emissions could end up reducing the world’s annual economic output by somewhere between 5 and 20 percent by 2050. The cost of staving off the worst effects, by contrast, would reduce annual economic activity by between 1 and 3.5 percent by 2050.