10 April 2008

The refutation of nonsense

Unfortunately for future generations, the idea that “global warming stopped in 1998” seems to be gaining credence in the popular imagination. The claim is that the 'global warming hoax [has been] exposed by record global cold'. These are dangerous thoughts that need to be vigorously countered with proper data analysis which accounts for the physical behaviour of the climate system.

The claims are nonsense that is at odds with what the data show. The indicators are clear –- anthropogenic climate change is a reality which isn't going away, no matter how much we may wish it to be so.

Consider the image which shows a time series of the NASA GISS annual globally-averaged temperature anomalies. Where is the lack of warming since 1998? I just don't see it. The general trend is generally ever-upward, as it has been since the mid-1970s. It is true that this year is expected to be cooler than the previous few years. It's part of the interannual variability. The recent past has been characterized by a cold Pacific ocean associated with a strong La Nina event. January and February were quite cool over parts of the globe, with unusual snow amounts and occurrences reported in some regions. But northern Eurasia experienced well above normal temperatures during these two months, and the data for March indicate that most land areas are now running well above normal. The La Nina is rapidly breaking down, and neutral conditions are returning to the Pacific.

That said, other 1-2 year periods of 'global cooling' are easily visible in the data. When the next El Nino comes -- perhaps as early as 2009-- we will likely return to record-high global mean temperatures. It's only a matter of time. Excluding the data north of about 60 N will also give an apparent 'leveling off' of temperatures and the 'no warming since 1998' idea gets 'validated'...but what exactly is that supposed to tell you? If global temperature is desired, the whole globe needs to be considered...

The apparent recovery of sea ice in the Arctic is also being used to cast doubt on the reality of climate change. After reaching record low extents in September 2007, the ice area has 'recovered', apparently providing proof of the 'hoax'. Time series plots (at left) of Arctic sea ice anomaly from Cryosphere Today, show this to indeed be the case. The ice has recovered all the way to the areas (also anomalously low) seen in 2005. Wow! The ice came back during the long polar night. Before we start making grand pronouncements about the non-validity of climate change, can we at least wait and see what happens this year (and preferably a few more after that...)? The long polar summer has just begun. Ice extent won't reach a minimum again until September. It's also true that Antarctic sea ice has been anomalously high. But there is no reason to expect a symmetric response between the hemispheres. Paleo-climate studies indicate that quite clearly.

Make no mistake, humans are affecting the climate system. The link between increasing CO2 concentrations (35% and rising!) and enhanced greenhouse warming is undeniable. It is foolhardy to do so, and this is tantamount to what climate change deniers are doing. Exactly what the effects are going to be remains uncertain, but the early indications (as detailed here on planet doom?) are not positive. Acting now to prevent the (likely) worse effects to come is crucial; when The Cataclysm occurs, it may well be too late. The source of our environmental problems is our lifestyle and the society we have created. We have reached the limits to growth; the neoliberal philosophy is bankrupt. It's time to pay the piper. Techno-solutions will ease the way, but ultimately a lifestyle change will be required to create a lasting solution.

Images: NASA GISTEMP and Cryosphere Today, links above

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