This is a guest post by Climate Nexus.

Syndicated columnist George Will’s latest piece, “Climate change’s instructive past” is more carefully written than previous columns (see Media Matters Misinformer of the Year), but it still requires correction. Contrary to his claim, past changes in our climate should be understood as a warning, but shouldn’t be seen as evidence that current climatic change is naturally occurring, as he suggests.

The problem with this claim is that human-made emissions have increased exponentially since Will’s historical examples.  Science has clearly shown how current human-made climate change is very different from earlier slower natural changes, something Will failed to factor.

More accurately, historical climate change provides insight into problems we can expect in the future as greenhouse gases are increasingly amplifying variations in our climate. Historical trends should, instead, serve as a stark warning of what we can expect from the emission-driven warming we’re experiencing now.

Will reviews two books on historical climate change, one on the Medieval Warm Period (MWP) and another on the Little Ice Age (LIA), and suggests, inaccurately, that current changes are unexceptional in comparison. The fact is that while natural changes have always occurred, there are multiple independent lines of evidence showing humanity’s increasing influence on the climate:

• The Earth is warming at a pace not seen in 65 million years, and temperatures are higher than they have been in at least 1,700 years; and
• Observations, models and statistical tests all independently show a human footprint on current warming.

Additional factors that weren’t considered or included in Will’s analysis:

Current warming is unique: Current warming of the climate is historically unprecedented in pace and scale. The temperature record clearly shows that previous periods of change, including the MWP and LIA mentioned by Will, happened much more gradually than current temperature spikes. The climate is currently changing much faster and the changes are more substantial and pose even greater threats than those of the past. Changes happening even more rapidly will not be any easier for humanity to survive.

Human activities are causing warming: Scientists are confident of human responsibility for the warming we are experiencing and have reached this conclusion through attribution studies that assess the influence of different drivers of climate change, known as forcings. By comparing different forcings (both human-caused like deforestation, CO2 and other greenhouse gas emissions, and natural forces like the brightness of the Sun or Earth’s orbit around it) against observed changes, scientists can identify the influence of each component. The pattern of observed 20th century climate change clearly implicates human-caused greenhouse gas increases. This means, while natural forces have caused rapid climate change in the past, humans are now the primary drivers.

Even more illustrative is the fact that as the lower atmosphere (troposphere) is warming, the upper atmosphere (stratosphere) is cooling. This is because greenhouse gases accumulate in the lower atmosphere, trapping heat and preventing it from rising and warming the stratosphere. This is a phenomenon unique to greenhouse gas-driven warming and proof that the current warming is unnatural. The last time concentrations of CO2 were this high, seas were 100 feet higher and humans didn’t exist (2-4.6 million to 15 million years ago.)

Statistical studies have come to the same conclusion regarding human responsibility for current climate change. One recent study looked at the possibility that warming was solely natural, as Will suggests, and concluded instead that “we may reject the natural variability hypothesis at confidence levels >99%.” A look at the science shows that there is no reason to doubt the human-made nature of current climate change.

Will’s column clearly evokes a line of argument that deniers and delayers have been pushing for years, and, like them, he fails to heed the warning of science and history.