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THE ONGOING CONTROVERSY ABOUT CLIMATE CHANGE CONCERNS THE LONG-RANGE FUTURE, making it difficult to construct definitive indicators (as opposed to endless computer models) for the present. Too much of the public discourse on climate change focuses on “signs and wonders,” such as drowning polar bears, migrating armadillos, strong storms, heavy rainfall and/or drought, and unseasonable temperatures. Such signs and wonders, though of interest, do not constitute data and can be misleading.

For example, the eastern United States basked in record warm temperatures in late December 2006 and early January 2007. (This after Buffalo experienced its sixth heaviest snowfall in history—in October.)

Meanwhile, growers in California suffered $1 billion in citrus crop losses due to the coldest weather in 70 years. Climate change, perhaps, but is it global warming? It is useful to keep in mind that these seemingly interchangeable terms are not necessarily co-terminous.

The sole objective indicator of global warming is the overall average temperature. The National Climatic Data Center (NCDC) reported in early January 2007 that 2006 was the warmest year on record in the United States, edging out 1998, which held the previous record for both national and global temperatures.

The global temperature story was slightly less dramatic, with 2006 ranked as the sixth warmest year in the last 10 (and therefore the sixth warmest since 1900); however, because of the margin of error in the instrumental readings, both 2005 and 2006 are statistically indistinguishable from 1998. Does this temperature plateau of the last 10 years suggest that the warming trend of the last 30 years is moderating? A few scientists, including some from the Russian Academy of Sciences and two Chinese scientists, argue that the warming trend is, in fact, slowing, and they predict that a cooling period is about to commence, similar to what was experienced globally from 1940 to 1975.
Clearly, there has been warming, but, as mentioned elsewhere in this rambling blog, it appears to be stalled. What awaits is anyone’s guess.

Figure 2 displays the trend in global CO2 concentration in the atmosphere, taken from the monitoring series of the Mauna Loa Observatory in Hawaii. This time series is often shown on a narrow y-axis scale, such that the increase in CO2 appears steep and rapid, “alarming” even. (Sometimes very long-term CO2 levels are depicted on a logarithmic y-axis scale that produces even more dramatic but misleading imagery.) Here the trend is displayed on a wider y-axis scale, with two benchmarks to note the pre-industrial level of atmospheric CO2 and the level representing a doubling of CO2 (about 550 ppm), which has become the arbitrary target for carbon stabilization at some future point, beyond which it is presumed—though far from proven—that dramatic harm to the planet will occur.

Figure 2 makes evident an important fact typically left out of discussion: it has taken 200 years to go a little more than one-third of the way toward a doubling of CO2 levels in the atmosphere. Moreover, since close monitoring began in the late 1950s, the increase has been steady, at an average of 0.41 percent per year, or about 1.5 ppm per year. The rate has increased only slightly since global economic growth started accelerating in the 1980s. At these rates, it will be well into the 22nd century before the CO2 level reaches twice its preindustrial level.