A flaming stand-up argument, a sulky ignoring, a two-faced seeming agreement undermined by continued belief in the opposite opinion. There are many ways for people to disagree – and when it comes to climate change, surely all of them have been used. These disagreements can be good. Through them the human race progresses, with some people proposing ideas and others questioning and finding holes in them until they are well refined and hard to break down.
Over the past year, I have been writing about the latest climate research, and asking the scientists doing it questions on this blog. In that time I’ve learnt a lot about global warming, and it has become clear that the evidence showing that it is happening is robust enough to stand aggressive questioning. Most recently, it’s become more clear to me that the science on which predictions of how our behaviour will continue to affect climate is also well established, even though it is still being questioned and further refined. It’s right that we question it, but where the scientists I have been in touch with differ is in the fine details rather than on the overall picture.
That’s shown, in part, by the fact that many of the explanations of climate change that the scientists have given me are similar. In the past month Simple Climate readers have been voting to choose between them to help with one aim I had for the blog when I set it up in January: to produce a single, simple explanation of climate change. It’s fitting that the ultimate winner is one of the world’s leading climate researchers: Kevin Trenberth, head of the Climate Analysis Section at the US National Center for Atmospheric Research in Boulder.
His explanation was:
The Earth is habitable because of a natural greenhouse effect brought about mainly by water vapor (60%) and carbon dioxide (26%). Otherwise its average temperature would be below zero Fahrenheit. Humans are altering the composition of the atmosphere, mainly by burning fossil fuels. As a result carbon dioxide has gone up over 35% since pre-industrial times and over half of that is since 1970. This changes the greenhouse effect and traps radiation that would otherwise escape to space, producing warming. The warming is manifested in many ways, not just increasing surface temperatures, but also melting ice, and changing the hydrological cycle and thus rainfall. Since 1970 the effects are large enough to be outside the bounds of natural variability for global mean temperatures, but global warming does not mean inexorable increases in temperature year after year owing to natural variability.
I had thought that it might be necessary to merge different explanations, combining descriptions of the physical effects like this one with comments on the results of climate change. However, given the overwhelming majority that this answer gained in the final poll (over three-quarters of the votes) it seems fitting to use it as that one ultimate simple climate change explanation.
If you take one thing away from this blog, I would be happy if you absorb and understand that explanation. But over the year I have also been covering how research is advancing our understanding of climate change and what can be done about it. Some findings can contradict each other: that’s all a part of how science’s big argument helps humanity understand more. Even though I have now achieved my aim of a single explanation, I will continue to cover the emerging evidence right here every week.
What I’ve covered so far makes a convincing, perhaps even daunting, case. Climate change is serious – if it progresses far enough it will cause problems ranging from interfering with food supplies to death. Yet, despite that, I feel that there still remains hope. Global warming can be slowed if we cut our greenhouse gas emissions, and that can be done. If you take two things away from this blog, make that the second – and preferably encourage your friends, family and politicians to do something about it.