August 02 ,2013
The Receding Threat of Global Warming
A few weeks ago President Obama gave a major address on climate and energy policy and committed his administration to dealing more aggressively with the issue, which cheered liberals and environmentalist who see global warming brought on by carbon dioxide emissions from fossil fuels as the major problem of this century. While they are right to be concerned, the problem is turning out to be not quite so big and more easily manageable than was thought even a few years ago.
The science of global warming is based on the idea that carbon dioxide, which is produced by burning coal, oil, or natural gas, traps heat against the Earth’s surface, and raises the temperature enough to affect the climate. Even with all the fossil fuel burned in the last hundred years, we have only increased CO2 from .03% to .04% of the atmosphere, which seems fairly trivial, but computer models suggest that it is enough to alter the Earth’s temperature. If the concentration of CO2 were to double, some projected that the Earth could warm by 5 degrees centigrade, which would melt the ice caps and raise sea levels a dozen feet or more. Meanwhile, no country seemed ready to give up fossil fuels, which are critical for electric power, heating, and transportation. The modern world runs on massive amounts of cheap energy from coal, oil, and gas.
In the last few years though, three major trends have taken hold that suggest we are not doomed. First, though the Earth has warmed over the last thirty years in response to rising CO2 concentrations (and because it is such a rare gas, we use PPM or parts per million to describe the level), it has not warmed as fast as the climate models predicted. There are over 35 of these models, but they all predicted more warming than has happened. This suggests the climate is not as sensitive to the rise in CO2 as was earlier suggested. The UN based IPCC (which is the definitive scientific body that addresses climate change) is issuing their next assessment shortly, and it seems they have reduced the temperature rise predicted for 2100. If we keep CO2, currently at 400 PPM, to a level of 550 PPM, then temperatures are expected to rise less than the 2 degrees centigrade considered “acceptable” climate change (about .5 degrees of that has happened already since 1980). Even if levels get to 710, the expected temperature rise is between 2.3 and 3 degrees.
This suggests that we could accept CO2 going as high as 550 PPM or maybe a bit more. This leads us to our second favorable trend. Currently, humanity is emitting 9.6 gigatons of carbon (gTC) per year, a rate that rose at about 2.5% per year for the last 15 years. To put that into perspective, we have to emit about 4 gTC to raise CO2 by 1 PPM. But much of that rapid rise was the vast expansion of coal used in China. It was not the developed world. In fact, European emissions peaked in the mid-1990s, and the US peaked in 2007. US emissions have plunged in the last three years and are down to 1992 levels, primarily due to rising fuel efficiency and the switch from coal to natural gas in power plants. Meanwhile, China’s ultra rapid growth is finally subsiding. With demand in the developed world declining, and China slowing down, the growth in CO2 emissions going forward is going to subside. The doomsday scenarios that the UN IPCC predicted in the 1990s suggested annual CO2 emissions might go as high as 30 gTC by 2040, but such a future looks very unlikely now. If we want to keep peak CO2 at 550 PPM, the rough math suggests we need to keep total emissions going forward to less than 600 gTC. Given current emissions and likely growth rate, we have 40-50 years to stop burning fossil fuels. That is doable.
The reason it is doable is the third major trend. This is the rapid plunge in the cost of renewable “green” power, namely solar and wind, but also potentially geothermal. Already, solar power is as cheap as regular grid power in sunny climates with expensive electricity (Hawaii, Southern California). In another 10 years, solar will be as cheap as fossil fuel sources in many parts of the world. Cars are rapidly becoming more fuel-efficient and electric and hybrid cars are gaining popularity. How soon will we have an all-electric auto fleet? 20 years? 30 years? It will happen, and faster than expected. Wind is cost-effective power in many regions. The main problem with solar and wind is “intermittency”, meaning that power can’t be generated at night or when the wind isn’t blowing. But clever energy storage solutions will solve that problem over the next two decades. I imagine that no new fossil fuel-based power plants will even be built after 2025 or 2030 anywhere in the world, because renewables will be cheaper.
Is there an emergency exit, a way to rapidly decarbonize the energy systems if it turns out that we start to warm more rapidly, or that 550 PPM is too high a level to accept? Yes there is, it is nuclear power. Traditional nuclear power, using uranium, is extremely expensive, and carries both radiation risk (such as the disasters at Chernobyl in 1986 or Fukushima in 2011), and weapons proliferation risk. There is another radioactive element that can power reactors that is even more abundant than uranium and has much less radiation hazard and no weapons risk; that would be thorium-based reactors. Thorium is an abundant radioactive element, and can work as a fuel in a nuclear power plant. A global replacement of coal and gas plants with thorium reactors in the 2030’s could be the world’s emergency chute if all else fails. It would cost a lot to mothball working power plants and replace them, but the world will also be twice as rich as we are, and they can afford it.
Politically, the nations of the world should commit themselves to definite physical goals. We should commit to keeping CO2 levels below 550 PPM, and to keep the total temperature rise to under two degrees centigrade. We should also revisit and revise the 550 PPM number downward if trends suggest that would not contain warming as the IPCC now expects. We could even conceivably let the 550 PPM number go a bit higher if warming is slower than expected in the next two decades.
