What do the naysayers say? In the popular press, an outspoken, well-respected columnist who consistently downplays the effects of CO2 on global warming— and indeed denies any global warming—is George Will. He claims that there has been no global warming since 1998, that the models that predict global warming are based on “dicey” assumptions, and that scientists are likely to be wrong about global warming, since they also predicted global cooling in 1975 (12). He loves to quote the April 28, 1975, cover story of Newsweek called “The Cooling World” as evidence that scientists don’t know whether the earth is warming or cooling. However, that Newsweek article did not represent the consensus of scientific articles at the time.2 The best way to evaluate these claims is to look at some actual data on temperature and CO2 levels, which we will do shortly.

Many politicians have been vociferous opponents of the science of global warming. Perhaps the most vocal is Senator James Inhofe from Oklahoma, who said in a January 4, 2005, statement on the Senate floor:

As I said on the Senate floor on July 28, 2003, “much of the debate over global warming is predicated on fear, rather than science.” I called the threat of catastrophic global warming the “greatest hoax ever perpetrated on the American people,” a statement that, to put it mildly, was not viewed kindly by environmental extremists and their elitist organizations. I also pointed out, in a lengthy committee report, that those same environmental extremists exploit the issue for fundraising purposes, raking in millions of dollars, even using federal taxpayer dollars to finance their campaigns. (13)

In his view and that of other (mostly Republican) politicians with similar beliefs, this is all a hoax perpetrated by environmentalists. Other politicians, such as the British politician Nigel Lawson, have a more nuanced view but still are convinced that the ultimate consequences of any global climate change are small compared to the economic cost of doing anything about it when there are more pressing human needs (14).

Another common criticism is that if weather forecasters can’t predict the weather accurately within a few days, how on earth can models predict the cli­mate for 50 years in the future? But this argument confuses the difference between weather and climate. Weather is the daily temperature, precipitation, and storm activity, which varies widely over time and geographical areas. The differences between weather and climate are clearly explained in the fourth IPCC report in 2007:

Climate is generally defined as average weather, and as such, climate change and weather are intertwined. Observations can show that there have been changes in weather, and it is the statistics of changes in weather over time that identify climate change. The chaotic nature of weather makes it unpre­dictable beyond a few days. Projecting changes in climate (i. e., long-term average weather) due to changes in atmospheric composition or other fac­tors is a very different and much more manageable issue. As an analogy, while it is impossible to predict the age at which any particular man will die, we can say with high confidence that the average age of death for men in industrialised countries is about 75. (15)