New Evidence Confirms Land Warming Record

State of the World Forum’s Paul Ray forwards this piece and reminds us of this a key social-political point: The anti-science climate denial campaign is being coordinated by the same PR firms that coordinated the cancer-denial campaign for the tobacco companies. This time they’re doing it for the oil and coal companies. And for the Saudi Arabian government. For those of us with long memories, that’s why there’s a sort of familiar ring to their attempt to create confusion about what the science says, and to employ anti-science ideologues.

Joe Romm

Everybody but the anti-science disinformers has known for a long time that the Hadley/CRU (Climatic Research Unit) temperature data UNDERestimates — not OVERestimates — the recent global temperature rise.  Why?

“There are no permanent weather stations in the Arctic Ocean, the place on Earth that has been warming fastest,” as New Scientist explained (see here and here). “The UK’s Hadley Centre record simply excludes this area, whereas the NASA version assumes its surface temperature is the same as that of the nearest land-based stations.” Thus it is almost certainly the case that the planet has warmed up more this decade than NASA says, and especially more than the UK’s Hadley Center says.

I’ve repeatedly written about this (see “What exactly is polar amplification and why does it matter?“ and here).   So has NASA’s James Hansen (see below).

Mean temperature difference between the periods  2004-2008 and 1999-2003 RealClimate has an excellent post on this very subject — “the ‘hole in the Arctic’ in the Hadley data, just where recent warming has been greatest” — with this great figure (and caption):

Figure. The animated graph shows the temperature difference between the two 5-year periods 1999-2003 and 2004-2008. The largest warming has occurred over the Arctic in the past decade and is missing in the Hadley data.

See also “Human-caused Arctic warming overtakes 2,000 years of natural cooling, “seminal” study finds.”

Thus contrary to what the global warming disinformers say about the recent temperature record, it is almost certainly the case that the planet has warmed up more this decade than NASA says, and especially more than the UK’s Hadley Center says.

In December, the Met Office admitted as much with a new analysis published on their website:

New evidence confirms land warming record

18 December 2009

New analysis released today has shown the global temperature rise calculated by the Met Office’s HadCRUT record is at the lower end of likely warming. The study, carried out by ECMWF (the European Centre for Medium-Range Weather Forecasts) with input from the Met Office, performs a new calculation of global temperature rise. This independent analysis is based on information from a wide range of sources. It  uses all available surface temperature measurements, together with data from sources such as satellites, radiosondes, ships and buoys.

The new analysis estimates the warming to be higher than that shown from HadCRUT’s more limited direct observations. This is because HadCRUT is sampling regions that have exhibited less change, on average, than the entire globe over this particular period. This provides strong evidence that recent temperature change is at least as large as estimated by HadCRUT. This conclusion is in contrast to a recently released study by the Institute of Economic Analysis (IEA) think tank based in Moscow. The IEA’s output is consistent with HadCRUT as they both confirm the global warming signal in this region since 1950, which we see in many other variables and has been consistently attributed to human activities

Increase in mean near-surface temperature (°C) from (1989-98) to (1999-2008)

Increase in mean near-surface temperature (°C) from (1989-98) to (1999-2008)
The lower figure is the ECMWF analysis which uses all available observations, including satellite and weather balloon records, synthesised in a physically- and meteorologically-consistent way, and the upper figure represents the same period from our HadCRUT record. The ECMWF analysis shows that in data-sparse regions such as Russia, Africa and Canada, warming over land is more extreme than in regions sampled by HadCRUT. If we take this into account, the last decade shows a global-mean trend of 0.1 °C to 0.2 °C per decade. We therefore infer with high confidence that the HadCRUT record is at the lower end of likely warming.

I would say, “Duh” but apparently even stuff that has been obvious in the scientific literature is missed by the media and ignored by the antiscience crowd.

How far back was this known in the literature?  As Hansen explained (again) — see NASA reports hottest November on record, 2009 poised to be second hottest year, Hansen predicts better than 50% chance 2010 will set new record:

As discussed by Hansen et al. (2006) the main difference between these analyses is probably due to the fact that British analysis excludes large areas in the Arctic and Antarctic where observations are sparse. The GISS analysis, which extrapolates temperature anomalies as far as 1200 km, has more complete coverage of the polar areas. The extrapolation introduces uncertainty, but there is independent information, including satellite infrared measurements and reduced Arctic sea ice cover, which supports the existence of substantial positive temperature anomalies in those regions.

If you want a debunking of the anti-science spin on the IEA’s work (by Delingpole!), see Deltoid’s 12/17 post, “Russian analysis confirms 20th century CRU temperatures.”

Here is the Met Office’s “Proposal for a New International Analysis of Land Surface Air Temperature Data.

Bottom Line:  I applaud the Met Office’s efforts to be more transparent about the temperature record — but even more important is for the Met Office to be more accurate.