Those who deny the reality of human-induced climate warning should mark their calendars. Today, climatologists reported a new prediction from their computer-based model of the planet’s climate. After folding into the model precise information about the state of the ocean and the atmosphere rather than the approximate parameters other models use, they find that global warming will slow during the next few years.
Just to emphasize: even as greenhouse gases accumulate in the atmosphere, other influences will keep the world from continuing on the upward temperature path it’s been on since the 1990s. No one ever said that the greenhouse effect is the only thing driving our climate, and from time to time other factors will outweigh it. We are moving into one of those times, say the British climatologists. So when 2008, say, turns out not to set any temperature records even though 11 of the last 12 years have done so, can we please not have press conferences and headlines and op-eds and Senate floor speeches saying, “see? That whole global warming thing was a hoax.” To the contrary. The same climate models that foresee the changes chronicled in the IPCC reports also say that we’re in for a few years of reprieve from the almost unrelenting temperature rise.
Climate models have been justly criticized for neglecting “internal climate variability,” a sort of climatic crapshoot that arises from natural changes such as El Niño and fluctuations in ocean circulation. Yet these and other influences can and do trigger short-term changes that are quite different from the overall warming expected over the next century as a result of the growing concentration of greenhouse gases in the atmosphere. In the new study, Douglas Smith of the Hadley Centre for Climate Prediction and Research in Exeter, U.K., describes an improved version of their climate model that predicts both internal variability and externally-induced changes such as the greenhouse effect, that will be reported in tomorrow’s issue of the journal Science. So, for instance, natural zigs and zags of, say, currents in the North Atlantic Ocean can set in motion effects that eventually lead to drought in Australia.
Natural “forcings” such as this have kept the full force of the greenhouse effect in check in recent years, they say. In other words, the amount of global temperature rise expected from the carbon dioxide and other greenhouse gases in the atmosphere is less than models predict—and the reason is that nature has been pushing in the other direction, to cool the planet. The power of global warming has been masked in recent years by natural variability.
But you can fool Mother Nature (or get her on your side) only so long. Once the natural cycles move into their next phase (about when the next president is inaugurated and the next Congress sworn in, as luck would have it), the warming “should come roaring back before the end of the decade,” as Science’s Richard Kerr puts it. Something to look forward to.