A June 21 Wall Street Journal editorial (subscription required) cited outdated statistics to claim that proposed legislation to limit fossil fuel emissions “seems entirely untethered to real science.” To bolster its claim that natural forces are responsible for a recent rise in global temperatures, the Journal offered a 15-year-old chart from the United Nations' Intergovernmental Panel on Climate Change (IPCC). More recent IPCC reports refute this chart's findings.
The Journal criticized the Climate Stewardship Act, proposed by Sens. John McCain (R-AZ) and Joseph I. Lieberman (D-CT), which would set 2010 as a target date for significantly reducing greenhouse gas emissions. The Union of Concerned Scientists has heralded it as “the most significant piece of climate change legislation to be introduced in recent years.”
The Journal claimed that “the case for linking fossil fuels to global warming has, if anything, become even more doubtful” in recent years. As evidence, the Journal presented a graph from the First Assessment Report of the IPCC, released in 1990 (not available online), which shows that global temperatures were higher 700 years ago than they are today:
So what would be a fair representation of how most scientists view the climate of the past 1,000 years? We'd suggest the graph nearby, which we reprint exactly as it appeared in the first report of the U.N.'s Intergovernmental Panel on Climate Change (hardly a group of oil-funded hacks) in 1990. It shows that our own warming period is neither unique nor all that hot.
The IPCC's Third Assessment Report, however, refutes this claim. The report features a graph similar to the one the Journal touted, but the more recent graph shows that since 1900, fluctuating surface temperatures in the Northern Hemisphere have spiked well beyond pre-industrial levels. The report credited increased amounts of data and technological advancements for its findings: “Since the SAR [Second Assessment Report, 1996], a number of studies based on considerably expanded databases of palaeoclimate information have allowed more decisive conclusions about the spatial and temporal patterns of climate change in past centuries.”
The Journal specifically mentioned two supposed climatic epochs labeled on the graph -- the “Medieval Warm Period,” and the subsequent “Little Ice Age” -- and claimed that these two global temperature shifts indicate that “the slight warming believed to have occurred in the past century could well be no more than a natural rebound, especially since most of that warming occurred before 1940.” The Third Assessment Report, however, found that global warming and cooling shifts were too varied during those time periods for them to be labeled trends. According to the report:
Thus current evidence does not support globally synchronous periods of anomalous cold or warmth over this timeframe, and the conventional terms of “Little Ice Age” and “Medieval Warm Period” appear to have limited utility in describing trends in hemispheric or global mean temperature changes in past centuries.
The latest IPCC report also found that the Earth's surface temperature rose by between 0.4 and 0.8 degrees Celsius over the past 100 years. Roughly half of that increase occurred from 1900 to 1940, at which point there was a slight cooling. But the second half of the increase occurred from 1980 to 2000, half the time it took for the initial rise.
The Journal further argued that the link between fossil fuels and temperature change is “even more doubtful” by attacking the research of a single geoscientist: University of Virginia professor Michael Mann. Mann developed the “hockey stick” graph, which shows little climatic temperature change until a drastic spike upward in the early 20th century. Though this graph has been criticized for its methodology and assumptions, as the Journal pointed out, the Third Assessment Report found that "[e]missions of greenhouse gases and aerosols due to human activities continue to alter the atmosphere in ways that are expected to affect the climate." A few sentences later, during its account of relevant “human activities,” the IPCC added: “About three-quarters of the anthropogenic emissions of CO2 to the atmosphere during the past 20 years is due to fossil fuel burning.” Mann was only one of scores of authors of the IPCC's Third Assessment Report. Hundreds of other scientists served as reviewers.