RealClimate: Unforced variations: March 2023

Victor says

22 Mar 2023 at 1:51 PM

nigelj says:

"US heatwaves- no long term trend."

nigel: Its plain to see an increasing trend from 1940 – 2020 so I’m not sure what Victor is looking at.

V: Here's what I’m looking at. From the EPA https://www.epa.gov/system/files/images/2022-07/heat-waves_figure3_2022.png

In the same paper that displays this graph. we find the following highly misleading assertion:

"Heat waves are occurring more often than they used to in major cities across the United States. Their frequency has increased steadily, from an average of two heat waves per year during the 1960s to six per year during the 2010s and 2020s"

Talk about cherry picking. They choose the 1960s as their reference point, the start of a period beginning in 1960 and continuing through 1980, where, according to the graph, there were hardly any heat waves at all. If you consider the entire graph, however, representing data from 1895 through 2020, it becomes clear that there is no long-term trend.

nigel: However the graph doesn't show us a GLOBAL trend so Victor is just cherry picking. Trends vary in different countries and only the global tend shows what global climate change is doing. Studies show that globally heatwaves have increased in frequency and intensity:

V: Ah yes, always with the "cherry picking." Just about every reference I could find was to heatwaves in the contiguous 48 states. I did, however, manage to find one very strange graph representing global data (https://ars.els-cdn.com/content/image/1-s2.0-S0048969716314516-fx1.jpg ) included in the following article: https://www.sciencedirect.com/science/article/abs/pii/S0048969716314516

Very strange indeed! Note the complete lack of any long-term upward trend — in fact we see a distinct downward trend from 1940 to just prior to 2000. From 2000 through 2010 (a period of only 10 years) we see a sudden leap where the whole thing seems to go haywire. Pardon me for finding this very odd leap highly suspicious. In any case it's not at all clear what this study is supposed to be telling us.

nigel: "Here, using the Berkeley Earth temperature dataset and key heatwave metrics, we systematically examine regional and global observed heatwave trends. In almost all regions, heatwave frequency demonstrates the most rapid and significant change. A measure of cumulative heat shows significant increases almost everywhere since the 1950s, mainly driven by heatwave days. Trends in heatwave frequency, duration and cumulative heat have accelerated since the 1950s"

https://www.nature.com/articles/s41467-020-16970-7

V: Interesting. I can't help noting the complete difference between the data displayed in this paper and the graph I alluded to above. Looks like results will vary depending on the methodology employed.

"Hurricanes. No long term trend"

nigel: Ryan Maues data and commentary is his own view and should be viewed with extreme caution. He was appointed to NOAA by the Trump administration and he has a history of climate science denialism.

V: So you’re suggesting he faked his data? Wow. That would be quite a scandal wouldn't it? Another climategate, perhaps?

nigel: The following is data on hurricanes: "Number of Category 4 and 5 Hurricanes Has Doubled Over the Past 35 Years, according to the National Science Foundation." They are a more credible source.

https://www.nsf.gov/news/news_summ.jsp?cntn_id=104428

V: Published in 2005. Isn't that a bit out of date? From an article in the Washington Post, 2017: https://www.washingtonpost.com/news/energy-environment/wp/2017/09/07/the-science-behind-the-u-s-s-strange-hurricane-drought-and-its-sudden-end/

"Since 2005 . . . we’ve experienced no major U.S. landfalls until Harvey this year. . . Before Hurricane Harvey, the continental United States had not been hit by a Category 3 or higher "major hurricane" for 12 years — dating all the way back to 2005's Hurricane Wilma."

". . . the question of whether storms are measurably stronger at present remains contested, with NOAA's Geophysical Fluid Dynamics Laboratory asserting that "it is premature to conclude that human activities — and particularly greenhouse gas emissions that cause global warming — have already had a detectable impact on Atlantic hurricane or global tropical cyclone activity." The effect could be there, NOAA said, but not yet clearly detectable in the statistics."

nigel: "Precipitation. No long-term trend"

The graph has no title, no location data, no source.

V: Sorry about that: https://climatedataguide.ucar.edu/climate-data/gpcp-monthly-global-precipitation-climatology-project

nigel: "Little change in global drought"

Victor cherry picks one single study on drought that suits his narrative. Numerous studies show changes in droughts "Climate change is making droughts more frequent, severe, and pervasive" according to NASA.

https://climate.nasa.gov/news/3117/drought-makes-its-home-on-the-range/

V: This article references relatively recent satellite observations, which tell us nothing about long-term trends.

nigel: "Human-caused global warming has made severe droughts like the ones this summer in Europe, North America and China at least 20 times as likely to occur as they would have been more than a century ago, scientists said Wednesday."

https://www.nytimes.com/2022/10/05/climate/climate-change-europe-drought.html

V: That's a newspaper article, not a scientific study. In any case it's behind a paywall so I can't (won't) review it, sorry.

"The intensity of extreme drought and rainfall has "sharply" increased over the past 20 years, according to a study published Monday in the journal Nature Water. "

https://www.pbs.org/newshour/science/scientists-confirm-global-floods-and-droughts-worsened-by-climate-change

V: Once again, this report references satellite data, telling us nothing about any possible long-term trend. The report I referenced covered a much longer period and revealed no such trend.

nigel: I could go on. The point is you have to look widely at several studies to be able to see the wood and not be distracted by the trees, as the saying goes. Victor relentlessly cherry picks, so just ends up fooling himself, and demonstrating nothing of value.

V: Reporting on perfectly legitimate, peer reviewed science published in reputable journals is NOT cherry picking. That's an all too easy out for those who, like you, refuse to accept that different methods can produce contradictory results — in other words, the science is NOT settled.

Regardless. What's much more important is the tendency I’ve seen over and over again in the alarmist screeds, both from the media and the climate scientists themselves. Those long lists of all the awful things that are supposedly happening due to global warming (aka "climate change") do NOT constitute evidence that the warming in question is being caused by CO2 emissions. Yet that's consistently been implied. This is both unscientific and dishonest. And as far as those "attribution studies" are concerned, they are all based on the prior assumption that CO2 and other greenhouse gases are heating the atmosphere and the oceans to a significant degree — which was to be demonstrated. Clearly an example of circular reasoning.