Well, is it warming or not?

Just as climate scientists finally succeeded in convincing everyone that global warming is imminent, the latest versions of their models seem to be leading them to take a more cautious line.

In May last year, a study led by Noel Keenlyside of the Leibniz Institute of Marine Sciences in Germany reported that due to multi-decade-long changes in ocean currents, "global surface temperature may not increase over the next decade, as natural climate variations in the North Atlantic and tropical Pacific temporarily offset the projected anthropogenic warming." This was significant enough for Nature to include it in their year-end summary of “What we’ve learned in 2008” (see the sixth item down: “How much warming and by when”).

Even the Hadley Centre for Climate Change in the UK is moving in the same direction, with new model revisions that factor in ocean temperature effects. The resulting temperature projection from the HadCM3 model shows temperatures fluctuating roughly around today's average level until about 2030, only beginning a predicted rise after that.

What are we to make of all this? One implication is that in any strategy scenarios for the next ten or twenty years, we should not be talking about higher average temperatures, but possibly even a cooling. And while climate change deniers are far from getting the upper hand, there seems to be an increasing acceptance that the situation is more complicated than we thought.