Two Degrees - Is It Possible?

The article at the link below talks about Obama trying to get countries at the G8 meeting to commit to reduce GHG emissions.

http://www.msnbc.msn.com/id/31823389/ns/world_news-europe/

He was not successful, but a couple of agreements were made:

“The Group of Eight nations — Britain, Canada, France, Germany, Italy, Japan, Russia and the United States — agreed at their summit in this central Italian town to a goal of cutting the world's greenhouse gas emissions in half by 2050, and emissions from their countries by 80 percent by then to help get there.”

“The rich and emerging nations also together declared for the first time that average global temperatures should not rise higher than 2 degrees Celsius above those of preindustrial times. But the leaders made no commitments to do anything in the near term, say by 2020, to reach that goal.”

Why is 2 degrees Celsius important?

“That's the point at which the Earth's climate system would fall into perilous instability, according to the United Nations' chief panel on climate change.”

In this posting I will try to answer a question I had when reading the above article: Will cutting the world’s GHG emissions 50% by 2050, yet not doing anything significant before 2020, prevent global temperatures from rising more than 2 degrees Celsius above preindustrial levels? My gut said probably not, but I wanted to see if I could get an idea based on the current science.

I first did my own rough analysis of the data, based on charts from the U.S. government’s report “Global Climate Change Impacts in the United States”, which you can find here:
http://www.globalchange.gov/publications/reports/scientific-assessments/us-impacts

I came to the conclusion that if we don’t do much before 2020, the best case scenario is that we will reach 500 to 550 ppm CO2 equivalent before leveling off, some time around 2100, and the temperature will reach around 2.5 to 3 degrees C above preindustrial levels. This assumes no feedback mechanisms kick in before then, although we know that some of them (especially the albedo feedback) have already begun, so it’s probably worse than that. But since this was a very rough estimate that I made by extending lines on graphs, I don’t know how accurate it is.

So let’s see what the IPCC says. A recent article (http://www.huffingtonpost.com/william-s-becker/grading-a-climate-bill-pa_b_240312.html) says, “The Intergovernmental Panel on Climate Change (IPCC) suggested that industrial economies would have to reduce emissions 25-40 percent below 1990 levels by 2020 to keep warming to 2 degrees.” It even says that reducing emissions this much only gives us a 50-50 chance of keeping warming to 2 degrees. If that is correct, then doing less than a 25-40% reduction by 2020 would be extremely foolish. And yet the Waxman-Markey bill the House just passed only aims to reduce emissions 3.6% below 1990 levels by 2020. Doing so little by then, as we and the world as a whole are currently planning, seems to guarantee that we will go above 2 degrees warming.

The article doesn't have references for these figures, but I found a web page that explains in detail where these they come from (various places in the 2007 IPCC reports): http://www.holmeshummel.net/2C-Target-Range.htm.

The scary thing is that the IPCC is often too cautious with their predictions, and their data is always a few years out of date. Some of my earlier postings on this blog contain specific examples, but one very relevant example is that by 2007, emissions had risen about half a gigaton (roughly 6%) higher than even the very worst scenario from the 2007 IPCC reports predicted!

And I discovered something else. A quote I found in a document coming from the Bali meetings shows that the 25-40% range for industrialized countries assumes that developing countries will reduce their emissions at the same time: "The ranges would be significantly higher for Annex I Parties if they were the result of analysis assuming that emission reductions were to be undertaken exclusively by Annex I Parties." As you may know, developing nations have so far refused to do anything at all until developed nations make significant reductions. See the third paragraph of this document: http://unfccc.int/files/meetings/cop_13/application/pdf/awg_work_p.pdf.

Now let’s see what an environmental group says. There is a report called “Climate Code Red”, put out by Friends of the Earth Australia in 2008, which you can find here:

http://itsgettinghotinhere.files.wordpress.com/2008/02/climatecodered_1.pdf

On page 5 it lists some global temperature numbers:

Global temperatures have already risen about 0.8 degrees C above preindustrial levels.
Another 0.6 degrees C will occur due to “thermal inertia”, even if no more GHG are released.
The albedo feedback, which is already happening, will add another 0.3 degrees C.

So we are guaranteed to go 1.7 degrees C above preindustrial levels, even if we stopped all emissions immediately. Of course that is impossible, so what is the best we can do? The same report says that another 0.4 degrees C will be added to the system by 2030 if emissions remain the same (as 2007 levels, I assume). If we continue current trends, emissions won’t stay the same, but will rise 60% by then. Since nobody is committing to do anything significant by 2020, that means the world as a whole would have to cut their emissions 60% below the “business as usual” levels in the 10 year period from 2020 to 2030 to keep the rise to 0.4 degrees C. The developing countries are demanding that the developed countries act first, so they probably will do nothing for at least the first 10 years. I don’t think the developed countries will reduce their emissions 60% in 10 years, much less reduce them enough to make up for the developing world. So I’m almost certain that more than 0.4 degrees C will be added to the system by 2030. So that means that temperatures will eventually reach 2.1 degrees C above preindustrial levels even if all the industrialized nations make a superhuman effort to reduce their emissions after 2020. In other words, we are already pretty much committed to pushing the climate into “perlious instability”. And these numbers still only take one of the many feedbacks (Albedo) into account, so it almost surely will be worse than this.

And that’s not all. There is a “global dimming” effect caused by the particles and water vapor that come from the same sources as greenhouse gases. This has been “masking” about half of the warming effects of greenhouse gases. When emissions are reduced, the particles and vapors will leave the atmosphere quickly, while CO2 will not. So as we reduce emissions, the global dimming effect will quickly disappear. This is expected to add at least an additional 1 degree C of warming (0.8 degrees from what exists now plus the minimum future increase of 0.4 degrees). In other words, when you take global dimming into account, the best case scenario is more than 3 degrees C above preindustrial levels, and that still ignores all the known feedbacks except one.

So it looks like we are probably headed for at least 3 degrees above preindustrial levels, or 2.2 degrees above current levels. My next blog will list some of the things that scientists predict might happen if warming reaches 2 degrees C and 3 degrees C above current levels.