Gov. Newsom Tweets Misleading Graph to Exaggerate California Warming

California Gov. Gavin Newsom (D) tweeted misleading and unverified information yesterday while attempting to score political points on climate change. Newsom claimed, “The evidence of climate change is all around us.” Instead, the evidence of Newsom’s attempts at spreading climate misinformation is all around us.

Newsom tweeted an image of a California temperature graph claiming 3 degrees of warming since 1980, along with the assertion, “There are no Democratic thermometers or Republican thermometers. The fact is — our average temperature has increased over the last 40 years. We’re experiencing record temperatures across CA. The hottest August on record. The evidence of climate change is all around us.”

It may be true that there are no Democratic thermometers or Republican thermometers, but Newsom proved there are politicians willing to misrepresent the thermometers.

If you examine below the graph that Newsom tweeted (see Figure 1, below), you will notice:

  • Newsom does not provide a source for the graph,
  • The “trend line” reflects a lower beginning temperature than it probably should,
  • The “trend line” reflects a higher ending temperature than it probably should,
  • The graph is not an annual temperature graph, but a “June – September” graph.

Because Newsom provided no source for the graph, we at Climate Realism pulled up the National Oceanic and Atmospheric Administration (NOAA) State Climate Summary for California. Figure 2, below, is a NOAA graph showing no recent increase in the frequency of hot summer days.


Figure 3, below, is a NOAA graph showing no recent decline in annual precipitation.

If we assume, for the sake of argument, that Newsom’s unsourced graph is accurate, the underlying data do not appear very alarming. As seen in Figure 4, below, NOAA documents that any increase in summer California temperatures is primarily due to temperatures not getting quite as cool at night, rather than any increase in daytime temperatures.

Of course, if climate change is the reason for any asserted increase in California temperatures, we should see a similar temperature increase beyond the state of California. NOAA in 2005 brought online the world’s most accurate network of temperature stations, with stations spread relatively evenly throughout the contiguous United States. As seen in Figure 5, below, the NOAA temperature network reports that there has been no warming in the United States since at least 2005. Any California warming during recent years is not reflected in the nationwide data and would appear to be an aberration, rather than signs of a wider warming.

In summary, Gavin Newsom tweeted an unsourced temperature graph that – even if it is accurate – captures just a small and misleading snapshot of California climate. Data from the National Oceanic and Atmospheric Administration show that if “the evidence for climate change is all around us,” it is evidence of a mole hill, not a mountain.

[Gavin Newsom photo courtesy of JD Lasic,, Wikimedia Commons]

James Taylor
James Taylor
James Taylor is the President of the Heartland Institute. Taylor is also director of Heartland's Arthur B. Robinson Center for Climate and Environmental Policy. Taylor is the former managing editor (2001-2014) of Environment & Climate News, a national monthly publication devoted to sound science and free-market environmentalism.

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