2009 Temperature

The Herald reports:

This year is likely to be among the 10 hottest years on record, early figures from the World Meteorological Organisation indicate.

As delegates gathered in Copenhagen for the second day of world climate negotiations, the WMO said average global temperatures from January to October placed 2009 about 0.44C above the long-term average – making it the fifth warmest year since instrumental climate records began in 1850.

The 10 warmest years on record have occurred since 1997, the WMO said.

The decade of the 2000s (2000-2009) was warmer than the 1990s, which were warmer than the 1980s.

I’ve been studying a fair bit of the raw data around average temperatures, and it is far more complex than one might assume, mainly because there is no actual way to calculate it, as the temperature varies every few kms. The spread of temperature stations is not even. In an ideal world you might have a measuring point every 100 square kms, but that is impossible.

That is why most of the data we read talks about the deviation from a long-term average. Because that doesn’t have to be spread evenly. If you use the same measuring place, you can accurately say the temperature at this point was higher in year x than the average of these years. And if you choose lots and lots of locations, and they are not hand picked to give you selected data, then it is fairly safe to say average temperatures are rising.

And that is fairly uncontroversial. Even amongst “skeptics” few people are saying the average temperature is not warmer. There is some talk of whether it has warmed since 1998, but that is useful to view in context.

The above graph I have created myself using the raw data on the web from three sources – the US National Climatic Data Centre (holds the world’s largest collection of climate data – they have 1.2 PB of digital data), NASA and the UK Met Office (the infamous Hadley).

Each centre compares to a different “average” period. The US NCDC compares to the century 1901 – 2000. NASA compares to the period 1951 – 1980 and the UK Met Office to 1961 to 1990.

They all show much the same direction, but not to the same magnitude. This is what one would expect. The graph does put post 1998 in context somewhat. 1998 was a very high year, and there is still an upwards trend – even if it has not yet exceeded 1998. The 2009 data is based on te monthly data for the first ten months of the year.

In yesterday’s thread there was a very good comment by Ben:

Global warming from GG emissions is the sum of two parts. First, a direct warming effect: a doubling of CO2 adds 1 to 1.5C to temperatures. No controversy there. But to get warming beyond that requires a second effect, positive net climate feedbacks, and the science on both the sign and magnitude of feedbacks is completely up in the air. About 80% of the IPCC’s 6.4C maximum warming depends on large positive feedbacks, which are completely unknown. It is not yet clear whether clouds and water vapor damp or add to underlying variation.

So there is consensus on direct effects, but on feedbacks, none at all.

I am not a scientist. But it is basic science that more greenhouse gases will increase temperature, if everything else remains constant. Ben says (I have not checked) that a doubling adds 1.5C. This is (as I understand it) uncontroversial and not disputed. This means that an option of do nothing is not particularly wise.

There is debate over whether there is “positive feedback” or not, and to what extent. Most scientists say there is, but this is not a case of something proven beyond dispute – it is based on models.

I have tended to take the formal IPCC reports as the most likely scenario. The stolen e-mails have damaged some of the credibility of IPCC processes – especially the boasting about making sure certain dissenting opinions are kept out. That really has rung some warning bells.

However even if one doubts this projections in terms of positive feedback, it is worth remembering there is really no doubt over the direct effects.

Where I think the debate should really be, is how much one spends on mitigation instead of adaptation. I do have real doubts that spending a trillion dollars or so globally on mitigation is sensible. Spending on adaptation may well be a better spend. However it is not quite a case of either/or but a mixture of both. Spending nothing at all on mitigation (ie never decreasing emissions) will result in inevitable temperature increases that will make life difficult in the future. Now this may not be in the next 100 years, but in the next thousand.

I have little time for those who claim that the world is doomed if by Xmas Eve there is not a decision to reduce emissions to a certain level by 2020.

But likewise I have little time for those who say it is all a giant conspiracy, and there is no need to do anything at all. I hasten to say that even prominent sceptics such as Ian Wishart do not hold that view. Almost every sceptic I know, says they are sceptical about how fast the planet is warming, and how much of it is due to mankind. Very few say that there is no warming at all, and that greenhouse gases are not contributing to that.