Friday, Nov. 3 saw the release of the Climate Science Special Report as part of the Fourth National Climate Assessment. The nearly 500-page examination of climate change evidence was intended to act as an “authoritative assessment of the science of climate change,” according to the report’s website. While it doesn’t include an assessment of the literature on climate change, which is a much-debated topic among skeptics, it does make one thing very clear: human activities are primarily responsible for the warming trends that have been observed since the Industrial Era started.
The Climate Science Special Report only reaffirms what we already know in this regard, but what some may find more startling is that it claims that climate models tend to be more conservative in their projections of the impacts of climate change.
According to the report, extreme heat and precipitation trends have been consistent with the expected response to a warming climate, but climate models have a tendency to underestimate just how extreme the observed trends are.
“While climate models incorporate important climate processes that can be well quantified, they do not include all of the processes that can contribute to feedbacks, compound extreme events, and abrupt and/or irreversible changes,”
the report states, “for this reason, future changes outside the range projected by climate models cannot be ruled out.” It is also stated that climate models are more likely to underestimate than they are to overestimate, due to the “systematic tendency of climate models to underestimate temperature change during warm paleoclimates.”
The idea that climate models underestimate the effects of climate change is not
new. Earlier this year, Brown University put out an article discussing the impacts of future temperature changes on tropical mountains such as Mount Kilimanjaro
and Mount Kenya in East Africa.
In June, NASA published an article about how estimated increases in precipitation due to climate change are also most likely too conservative. A scholarly article from 2013 titled “Climate change prediction: Erring on the side of least drama?” suggests that climate scientists are far from being guilty of alarmism and “overreacting to evidence of human impacts on the climate system.”
The tendency of climate models to underestimate means that we may have
even less time than previously thought to act in order to stay under 2 degrees Celsius (3.6 degrees Fahrenheit) of warming. The two-degree limit is “a rough target used by the United Nations to signal the point where dangerous climate change could begin,” according to an article in The Atlantic about the Climate Science Special Report.
The Climate Science Special Report states that limiting warming to this point will require a major reduction in carbon emissions and that achieving this reduction
in emissions must be done before 2030 if we are to stay within the two-degree limit. According to the report, “choices made today will determine the magnitude of climate change risks beyond the next few decades.”
The Climate Science Special Report is available for anyone to read and can be found at science2017.globalchange.gov
