Climate Change: Droughts
Post #995
NOTE: This post was inspired by the geo-scientist (Wielicki) who wrote this.
“The costs of carbon pollution are clear: decreasing crop yields, more destructive storms, the spreading of tropical diseases to temperate latitudes, rising seas, more climate refugees, failures of governance, increasing floods, deepening droughts, more destructive fires and heat waves -- all contributing to the new reality of the global climate crisis.”
—Al Gore, 30 Mar 2014
[emphasis mine]
When producing the film, An Inconvenient Truth (2006), Al Gore only had the 2001 IPCC report to go off of, so he may have accidentally thought that raising atmospheric carbon dioxide levels might increase the yearly count of droughts on Earth. Here is what he had for predictive purposes:
Using this restricted data set, it almost sort of does look like it might have been the truth that atmospheric carbon dioxide levels were causing a rise in drought. But the full data set tells the full story:
For over 20 years of data, atmospheric carbon dioxide levels kept rising, even at a rate that was a little faster than before, but droughts didn’t change.
The evidence suggests that, if you expand your time-window to more than 50 straight years of consecutive data, then the apparent relationship between atmospheric carbon dioxide and yearly droughts “goes away.” The evidence debunks that part of the film, An Inconvenient Truth, which stated that climate change causes droughts.
While the early data might have suggested that increased carbon emissions could cause drought, the full data set refutes that claim. Here is a scatterplot of values after the 2001 IPCC report:
With an R-squared value of just 0.0096 for the data after 2001 (rounded to 0.01 in the graph above), there is not even evidence of a “weak correlation” between atmospheric carbon dioxide (horizontal axis) and number of droughts per year (vertical axis). In order to reach the level of having weak correlation, you need at least 0.01+.
Reference
[longest-running dataset for atmospheric CO2] — NOAA. https://gml.noaa.gov/ccgg/trends/data.html
[weather events on Earth] — OWID. https://ourworldindata.org/grapher/natural-disasters-by-type