But, like similar scares in the past which ultimately came to naught, it seems that there isn't really any significant warming occurring at all and that whatever is happening to our climate, if anything, it's by no means clear that humans have anything to do with it.
A recent article in The Economist, a journal which has been sympathetic to the global warming alarmists, makes the point:
Over the past 15 years air temperatures at the Earth’s surface have been flat while greenhouse-gas emissions have continued to soar. The world added roughly 100 billion tonnes of carbon to the atmosphere between 2000 and 2010. That is about a quarter of all the CO₂ put there by humanity since 1750. And yet, as James Hansen, the head of NASA’s Goddard Institute for Space Studies, observes, “the five-year mean global temperature has been flat for a decade.”In other words, the skyrocketing temperatures predicted by Al Gore and illustrated by the alarming hockey stick graph simply aren't happening and climatologists don't have a good explanation as to why.
Temperatures fluctuate over short periods, but this lack of new warming is a surprise. Ed Hawkins, of the University of Reading, in Britain, points out that surface temperatures since 2005 are already at the low end of the range of projections derived from 20 climate models. If they remain flat, they will fall outside the models’ range within a few years.
The mismatch might mean that—for some unexplained reason—there has been a temporary lag between more carbon dioxide and higher temperatures in 2000-10. Or it might be that the 1990s, when temperatures were rising fast, was the anomalous period. Or, as an increasing body of research is suggesting, it may be that the climate is responding to higher concentrations of carbon dioxide in ways that had not been properly understood before. This possibility, if true, could have profound significance both for climate science and for environmental and social policy.
The top graph above shows the projected sharp, "hockey stick" rise in global temperatures that had been expected over the last decade. The bottom graph shows the actual data.
The models used to predict disaster seem to be inaccurate and several competing models show much less dire effects from atmospheric CO2. The Economist also points out that temperature fluctuations may be due to natural causes whose effects had been underestimated while the consequences of human activity have been overestimated:
the anthropogenic global-warming trends might have been overestimated by a factor of two in the second half of the 20th century.” It is possible, therefore, that both the rise in temperatures in the 1990s and the flattening in the 2000s have been caused in part by natural variability.What conclusions should we draw from this? The first is that Al Gore has made himself very rich by frightening people into believing on the basis of very ambiguous evidence that the apocalypse is nigh.
The second is that drastic government programs that would wreak havoc on national economies and industries in order to mitigate CO2 emissions are at best premature and perhaps unnecessary.
The third is that it's prudent to be open-minded but skeptical of claims of impending disaster when the evidence the claims are based upon allows several different interpretations.
It may be that human activity is creating a perilous environmental situation, but, Mr. Gore's books notwithstanding, the evidence is far from conclusive and there's certainly no warrant for panic or economically ruinous efforts to prevent something that we don't know is happening, don't know we're causing if it is happening, and don't know what its effects would be.