Did global warming end in 1998?
“There has been no recorded global warming for more than a decade, or one-third of the span since the global cooling scare.” George Will, February 15, 2009
"This whole idea of global warming, I'm glad that's over. It's gone. It's done. We won. You lost. Get a life!" Senator James Inhofe.
There are two main compilations of global temperature measurements: the NASA Goddard Institute and the Climate Research Unit of the University of East Anglia in the UK. They use slightly different sets of temperature measurements so they get slightly different results. As shown, NASA finds 2005 to be the hottest year on record, whereas the CRU shows 1998 as the hottest. The NASA data include more measurements from the Arctic, where global warming is amplified, and therefore many regard the NASA data as superior. George Will uses the CRU set to back his now oft-repeated claim that global warming ended in 1998. Several points need to be noted:
As shown in the NASA chart, a ten year span can be too short to reflect the long term trend. One can find ten-year periods when temperatures rose, fell, or remained flat. But in spite of these short term changes, the overall temperature trend during the twentieth century was up. Moreover, if one claims that global warming ended in 1998, one ought to be able to explain why the continued increase in atmospheric carbon dioxide since then did not cause a concomitant temperature increase. What cancelled the greenhouse effect?
The ups and downs of the NASA temperature chart make it obvious that something other than atmospheric carbon dioxide concentrations affects global temperatures. Other factors include variations in solar activity, volcanic eruptions, atmospheric ozone, sulfur aerosols, and the El Niño-La Niña oscillation. 1998 saw a strong El Niño; in the last few years, La Niña has prevailed, but a new El Niño began in the fall of 2009. Land and atmosphere temperatures tend to be higher during El Niño years and cooler during La Niña years: that could explain why 1998 was warmer than the last few years. Scientists predict that the arriving El Niño will help push global temperatures to a new record in 2010 or 2011.
Globally, 2009 tied for the second warmest year on record. In the Southern Hemisphere, 2009 was the warmest on record. The first decade of the twenty-first century was the hottest decade on record.
To say that global warming is over ignores that global warming is global. (This discussion is taken from the excellent site, Skeptical Science.) To find out what is happening to the globe, one has to add up the heat content not only of the land and atmosphere, but of the oceans, the ice caps and sheets, and so on.
The chart above makes two things obvious: first, overall the earth has continued to warm right through the period at which global warming is alleged to have ended. Second, a small amount of heat transferred from the ocean to the atmosphere, which is what happens during an El Niño, could cause land and atmospheric temperatures to rise. La Niña has the converse effect.
The chart below shows how the amount of heat stored by the oceans has increased over the last few years:
Global warming did not end in 1998. It has not ended and is not going to end for at least the next several decades, even centuries. The question is whether we can act now to restrain the warming to no more than 2°C (3.6°F). For that goal, time is fast running out.
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