Last Friday, the UN’s Intergovernmental Panel on Climate Change (IPCC) released the hotly (pun intended) anticipated new climate report. It elevated its previous statement that global warming is caused by human activity from “very likely” to “extremely likely,” and predicted that the average global temperature will rise by 1.5 degrees Celsius over the 21st century. These cautious statements nevertheless succeeded in raising objections from a slew of conservative media including Fox and the Wall Street Journal, the latter of which questions: “If emitting CO2 into the atmosphere causes global warming, why hasn’t the globe been warming?”
It is true that over the past fifteen years the rate of global warming has slowed, but it is NOT true that “temperature has been flat for 15 years,” as the WSJ obtusely claims. Climate change doesn’t work in a smooth line–it is a collection of data that make up a trend. Even taking into account the slowing rate of warming, the global temperature still clearly shows an upward trend. In the first decade of the 21st century, average temp went down (2000-2001), then up (2001-2003), then down (2003-2004), up again (2004-2005), down (2005-2008), and up again (2008-2010). Despite the frequent up and down motion, the temperature increased from 2000 to 2010–and if you consider the data over the past century, the trend is indisputably clear. The global temperature has risen by 1.3 degrees F over the last hundred years, and the rate of increase over the last 50 years was twice that of the rate during the preceding 50 years. Furthermore, the average temperatures in North American in the past half century is higher than any other 50-year period going back 1,300 years.
The WSJ further embarrasses itself by mocking the cautiousness of the report, the fact that they only claim likelihood rather than certainty, and quipping, “It would have also been nice to see some humility from the IPCC” since the previous report in 2007 predicted that the Himalayan glaciers would melt by 2035. That fervor for integrity, humility, and authority is really rich coming from the newspaper of the finance industry, but let’s focus on the most asinine aspect of the criticism. Scientists of IPCC, some of the most rigorous minds in science today, cannot predict what the global average temperature will be in the future–at least not any more accurately than any economist or financial analyst could predict the GDP or unemployment rate. Climate scientists make predictions based on models, but no lab or computer models can replicate the myriad real-life factors and their permutations exactly. Carbon dioxide is the primary factor in global warming, but it is far from being the only factor: water vapor is a significant greenhouse gas, especially since more water will evaporate from the oceans from rising temperatures; nitrous oxide from fertilizers and fossil fuels; methane. These are likely to provide positive feedback which would accelerate global warming. On the other hand, there are other hard-to-predict factors that will provide negative feedback, or slow global warming: volcanic ashes or atmospheric dust can block the sun’s rays and promote cooling, for instance. Without creating a life-size replica of Earth, scientists cannot (with good reason) predict exactly what will happen.
Clearly what these conservative talking heads lack is the basic grasp of the scientific method–and humility. Let’s review what’s clear from the report, since knowledge is power:
1. Global warming is indeed happening, and it is caused by human activity.
2. Reducing CO2 emissions will likely reduce the rate of warming, but will not guarantee that it will stop global warming altogether.
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