February 10 ,2012
Can We Stop Global Warming?
Though we may still be facing a deep economic slump, the long-term issues facing this nation and the globe do not go away. One of the biggest is global warming, the concept that as we continue to burn massive amounts of fossil fuels, we will raise carbon dioxide levels in the atmosphere high enough to cause major climatic changes with severe impacts on the natural world and human civilization in this century. Global warming remains controversial, although the number of scientists who completely dismiss it is very, very, small. But the more complex questions of how much carbon will we emit this century, what is a safe level of emissions, and what precisely will happen to the climate if we go above that, are very debatable.
The IPCC, the international UN body that issues the definitive reports on global warming, does give some insight on some of these questions. They have projected scenarios for what will happen to human population, economic activity, and CO2 emissions till 2100. There are two principal scenarios they put forward.
The first is one in which the world continues to rely on fossil fuels, with coal playing a huge role in electricity production; this is called the A1F scenario. Their other scenario is one in which the world makes a concerted effort to deploy new technology and shift away dramatically from fossil fuels for energy; this is called A1T. In both scenarios, they expect global population to rise to almost 9 billion by 2050, then decline to under 8 billion by 2100. But the global economy is set to expand from 40 trillion dollars in 2000 to 62 trillion now to 300 trillion by 2050, and reach almost 900 trillion in 2100. In 90 years the world will be 15 times richer than it is today. That seems like a lot, but the global economy in the last century grew from 2 trillion to 40 trillion in a hundred years, despite two world wars, a Great Depression, and much of the world living in European colonies for the first 50 or 60 years. The IPCC scenario assumes 4% annual economic growth to 2050, then 2% per year till 2100, certainly reasonable. In 2100, the average person on Earth will have a standard of living more than twice that of the average American today.
Since 1990, global carbon emissions have grown 40%. What will happen in the next 90 years? Currently we are emitting around 8 gigatons of carbon per year (gTC). Under the A1F scenario, over 1800 gTC will be emitted in the next 90 years, but under A1T it will be around 800 gTC. However, the difference in the two scenarios doesn’t really become apparent for several decades. Under A1F we go to 11gTC annually in 2020, 23 gTC in 2050, and all the way to 30 gTC per year in 2100. Under A1T we go to 10 gTC in 2020, 12 gTC in 2050, and decline to only 4 gTC in 2100. The real difference is whether we start to sharply decarbonize electricity production around the world starting in 2025 and then complete the process by 2060 or 2070.
The US alone emits 1.5 gTC per year, but US emissions have been basically flat for the last ten years and will likely rise little or none over the next decade. Almost all emission growth is in rapidly developing nations like China, which is now the largest emitter at 2 gTC. To keep emissions down, we basically need to do two things, decarbonize electricity production, and reduce emissions from transportation, mainly cars. The US has 200 million vehicles that emit .5 gTC per year. If we raised gas mileage sharply not just in the US but around the world to 100 mpg, we could keep carbon emissions at a manageable level even when there are three billion cars, like we will have in 2050. If gas mileage were to be the same as current American, those cars would emit 7.5 gTC per year, but with 100 mpg we would be down around 2 gTC per year. Obama has rules in place to raise gas mileage to 54 mpg by 2025, so we are moving in the right direction.
Is it possible though to live in a modern industrial economy, and keep global emissions to 7 or 8 gTC per year? We can do that if we can make modern societies so energy efficient that we emit only 1 ton of carbon annually per person. While no modern society is that efficient, and Americans emit 5 tons per person, there are some interesting examples of efficiency. The French only put out 1.7 tons per person, because they rely so heavily on nuclear power for electricity, and their gas mileage is 30% better than America. The Japanese put out 2.3 tons per person. So it is possible to be rich and not too dependent on fossil fuels.
The problem of global warming is not insoluble. In fact we probably have another two decades before dramatic action is even needed. If the world can decarbonize electricity in 2030 to 2060 timeframe, and can raise vehicle efficiency dramatically, the problem will be overcome. Electric power will need to be generated by nuclear, solar, and wind, though with both solar and wind we will need excellent new power storage technology to smooth out fluctuations in the wind and to provide power at night. Also, by waiting till 2030 for dramatic action, we have time to study the problem further, and to spend money on energy research and development. A measured transition is best. Scotland, with ample wind, is going to zero-carbon electricity by 2020, and California will be getting 33% of its power from renewables by 2020.
The A1T scenario suggests that we can emit 800 gTC with minimal warming as a result. That much carbon will raise CO2 in the atmosphere to 550 ppm from 390 today. But some scientists claim that above 450 ppm we will see dangerous levels of warming. Over the next 20 years we should carefully monitor temperature trends and see whether there is any evidence of more rapid warming occurring. So far the pace has been rather slow, with temperatures rising about .15 degrees Celsius per decade. The catastrophic scenarios suggest total warming of 5 degrees Celsius, which would be much more rapid. We are not seeing any evidence of that. So far.
