Global warming – is it humanity’s fault?

The environment is the big topic of the moment. That seems only right – if we cannot survive on our planet, then nothing else really matters. I was inspired by this article to investigate the matter and try and come up with a considered opinion. Comments are very welcome (I will update the blog entry with any new information that seems to be well substantiated and relevant), but please read the whole article before you comment, and make sure any claims contained in your comments are well referenced. Here goes…

What we know

I don’t think anyone doubts that human activity has resulted in large amounts of CO2 being released into the atmosphere. A pretty convincing article on this is here; we know that CO2 levels are increasing and we know where the new CO2 is coming from.

We also know that the mean global temperature has risen by 0.6 degrees in the last 100 years. This seems to be abnormal. The World Meteorological Organization have said that “the increase in temperature in the twentieth century is likely to have been the largest in any century during the past 100 years.” (ref). There also seems to be agreement that continued increase in temperatures would be very bad for all.

Finally, there is an agreed model of how CO2 could increase global temperatures. That is the greenhouse effect, which I am sure we are all aware of, and is explained here.

Where it gets tricky

So far so good. The question is whether or not the increase in CO2 is a (primary) cause of the increase in temperature, and therefore whether a continued increase in CO2 will continue to cause an increase in temperature (or indeed whether a decrease in CO2 levels will necessarily slow the temperature increase).

A lot of attention has been focussed on Al Gore’s An Inconvenient truth, and the close correlation of CO2 levels and arctic temperatures over the last 200,000 years. It has been pointed out that while they are indeed closely related, CO2 levels lag behind global by approximately 900 years (ref). So it seems that not only does temperature cause the CO2 levels to change, but that the timescale of that change is much greater than any effect we could have experienced in the last century. Now this is a difficult subject but I am fairly convinced that the vast majority of people who use the ice core data to either support or deny manmade global warming are misusing the data. The data fits in with what climate models have predicted, and therefore can be used to support current climate models, but in themselves they do not substantiate or deny the claims of global warming. I take this to be the meaning of this article. Any responses to this?

Computer models

So it seems that the real evidence that can convince or dissuade us of manmade climate change are the computer models. As is nicely summarised here, the models now accurately ‘predict’ past and present climate. No-one can be certain that they will correctly predict future climate changes, but they are our best prediction. A well written article here is the clincher for me – the scientific consensus based on computer models seems to be that climate change is ‘very likely’ to be down to humanity, and that therefore bigger changes would result from a continued increase in CO2 emissions.

So there you have it. This is the direction that my research has led me. I would be very interested to hear your responses, but please make them thoughtful and referenced – slagging matches will get us nowhere.