Tag: Global Science Report

Heavy Rains Increasing, but Not Disproportionately So

Global Science Report is a feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”

A new paper has been published in the journal Geophysical Research Letters that examines trends in heavy rainfall amounts across the U.S. The paper is authored by Newcastle University’s Renaud Barbero and colleagues, and, to summarize, finds that the heaviest rainfall events of the year have been increasing in magnitude since 1951 when averaged across nearly 500 stations distributed across the U.S. (note: results from individual stations may differ from the general finding).

Someone with a critical eye might ask the real question, which is “how much?” That such a number does not jump out of this paper—a cynic would say—probably means it is very small. Read on and you will find the answer.

That rainfall on the rainiest day of the year is increasing is, of itself, hardly surprising considering that the total annual rainfall amount averaged across the U.S. has also been increasing during this same period (again, results from individual locations/regions may (and do) depart from this generality).

Changes in heavy rainfall like this are often luridly described as a “disproportionate increase” in extreme events, or that extreme precipitation increases are “worse than expected.”

Read All About It! Heat Dries Things Up!

Global Science Report is a feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”

No one doubts that much of the West, especially California, has been very droughty since the turn of the century, and that heat and drought are highly correlated. So it seemed surprising that it was big news last week that forest fires, which require dry fuel, are on the increase out there.

University of Idaho’s John Abatzoglou and Columbia’s A. Park Williams used a large family of climate models to calculate various indices of western aridity (they used eight different measures), which were then related to the burned-out area every year. About half of the increase since the mid-1980s was related to climate-modelled warming. The other half, they say, was from other causes, including natural variability. The authors also note that some forest management practices may be contributing to the increasing burn.

The notion that this much drying is caused by dreaded global warming is what made the papers.

Should we use models that can’t even get close to the real-world evolution of lower atmospheric temperatures in recent decades to determine how much climate change is human-caused? That’s what they did—assuming only warming that was not modelled was “natural.” To say the least, that’s a heavy logical lift when it is so clear that the models are predicting far too much warming in the lower layers.

It is all too human to not let some else’s work get in the way of your confirmation bias. So there’s no mention of another explanation for why it’s so hot and dry there. Writing in the same journal that the fire work was published in, the Proceedings of the National Academy of Sciences (PNAS), two other western researchers, James Johnstone and Nathan Mantua, demonstrated that virtually all of the temperature changes in California and the West are related to changes in atmospheric pressure patterns that occur with or without global warming. That was first published in 2014, but there is no reference to it whatsoever in the fire paper. 

Nor is there any reference to the most comprehensive study of western fires—some 33,000 of them—by Argentina’s Thomas Kitzberger showing that for centuries the distribution and frequency of western fires is related to well-known atmospheric patterns over  both the North Pacific and North Atlantic, not global warming. It too was published in PNAS, in 2007.

But we digress. Aridity is largely driven by temperature (warmth) and precipitation. Unfortunately, only two of their eight measures of dryness are very sensitive to rainfall variability.

Climate models have pretty much no skill in estimating precipitation. But they do predict warming, and western (particularly California and Arizona) temperatures are higher than they were. So, absent any precipitation data, they are guaranteed to paint a drying picture and therefore an increase in fire extent.  

The six aridity indicators that are not particularly influenced by precipitation instead are primarily temperature-driven. Not surprisingly, these show much greater increases in aridity than the other two.

Here’s an example from the heavily forested northwest states of Idaho, Washington and Oregon. One of the aridity indicators is the Palmer Drought Severity Index (PDSI), an old warhorse that has been used to assess long-term moisture status since it was first published in 1965 by Wayne Palmer, a scientist at the (then) U.S. Weather Bureau. 

Floods Not Increasing Across the U.S.

Global Science Report is a feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our “Current Wisdom.”

In our continuing examination of U.S. flood events, largely prompted by the big flood in Louisiana last month and the inevitable (and unjustified) global-warming-did-it stories that followed, we highlight a just-published paper by a research team led by Dr. Stacey Archfield of the U.S. Geological Survey examining trends in flood characteristics across the U.S. over the past 70 years.

Previous studies we’ve highlighted have shown that a) there is no general increase in the magnitude of heavy rainfall events across the U.S., and thus, b) unsurprisingly, “no evidence was found for changes in extreme precipitation attributable to climate change in the available observed record.”  But since heavy rainfall is not always synonymous with floods, the new Archfield paper provides further perspective.

The authors investigated changes in flood frequency, duration, magnitude and volume at 345 stream gauges spread across the country. They also looked to see if there were any regional consistencies in the changes and whether or not any of the observed changes could be linked to large-scale climate indices, like El Niño.

What they found could best be described largely as a “negative” result—basically, few departures from the a priori expectation (often called the null hypothesis) that there are no coherent changes in flood characteristics occurring across the U.S.  Here’s their summary of their research findings:

Recap of Hurricane Hermine and Global Warming

 Global Science Report is a feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”

For more than two weeks Hurricane Hermine (including, its pre-hurricane and post-hurricane life) was prominent in the daily news cycle.  It threatened, at one time or another, destruction along U.S. coastlines from the southern tip of Florida westward to New Orleans and northward to Cape Cod.  Hurricane/global warming stories, relegated to the hell of the formerly attractive by the record-long absence of a major hurricane strike on U.S. shores, were being spiffed up and readied for publication just as soon as disaster would strike.  But, alas, Hermine didn’t cooperate, arguably generating more bluster in the press than on the ground, although some very exposed stretches of North Florida did incur some damage.  

Like Jessie, Woody and Stinky Pete in Toy Story 2, the hurricane/global warming stories have been put back in their boxes (if only they could be sent to a museum!).  

But, they didn’t have to be. There was much that could have been written speculating on the role of global warming in the Hermine’s evolution—but it’s just not politically correct.

With a bit of thought-provocation provided by newly-minted Cato Adjunct Scholar Dr. Ryan Maue—one of the best and brightest minds in the  world on issues of tropical cyclone/climate interactions (and other extreme weather types)—we’ll review Hermine’s life history and consider what factors “consistent with” human-caused climate change may have shaped its outcome.

Taming the Greenland Melting Global Warming Hype

Global Science Report is a feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”

There is a new paper generating some press attention (e.g. Chris Mooney at the Washington Post) that strongly suggests global warming is leading to specific changes in the atmospheric circulation over the Northern Hemisphere that is causing an enhancement of surface melting across Greenland—and of course, that this mechanism will make things even worse than expected into the future.

We are here to strongly suggest this is not the case.

The new paper is by a team of authors led by Marco Tedesco from Columbia University’s Lamont-Doherty Earth Observatory. The main gist of the paper is that Arctic sea ice loss as a result of human-caused global warming is causing the jet stream to slow down and become wigglier—with deeper north-south excursions that hang around longer.  This type of behavior is referred to as atmospheric “blocking.”

If this sounds familiar, it’s the same theoretical argument that is made to try to link wintertime “polar vortex” events (i.e., cold outbreaks) and blizzards to global warming. This argument which has been pretty well debunked, time and time again.

Well, at least it has as it concerns wintertime climate.

The twist of the new Tedesco and colleagues’ paper is that they’ve applied it to the summertime climate over Greenland. They argue that global warming is leading to an increase in blocking events over Greenland in the summer and that is causing warm air to be “locked” in place leading to enhanced surface melting there. Chris Mooney, who likes to promote climate alarm buzzwords, refers to this behavior as “weird.” And he describes the worrysome implications:

The key issue, then, is whether 2015 is a harbinger of a future in which the jet stream keeps sending Greenland atmospheric systems that drive major melt — and in turn, whether the Arctic amplification of climate change is driving this. If so, that could be a factor, not currently included in many climate change simulations, that would worsen the ice sheet’s melt, drive additional sea level rise and perhaps upend ocean currents due to large influxes of fresh water.

As proof that things were weird over Greenland in recent summers, Tedesco’s team offers up this figure in their paper:

<--break- >

This chart (part of a multipanel figure) shows the time history of the North Atlantic Oscillation (NAO—a pattern of atmospheric variation over the North Atlantic) as red bars and something called the Greenland Blocking Index (GBI) as the black line, for the month of July during the period 1950-2015. The chart is meant to show that in recent years, the NAO has been very low with 2015 being “a new record low of -1.23 (since 1899),” and the GBI has been very high with the authors noting that “[c]oncurrently, the GBI also set a new record for the month of July [2015].” Clearly the evidence is showing that atmospheric blocking increasing over Greenland which fits nicely into the global warming/sea ice loss/wiggly jet stream theory.

So what’s our beef?

A couple of months ago, some of the same authors of the Tedesco paper (notably Ed Hanna) published a paper showing the history of the monthly GBI going back to 1851 (as opposed to 1950 as depicted in the Tedesco paper).

Here’s their GBI plotted for the month of July from 1851 to 2015:

This picture tells a completely different story. Instead of a long-term trend that could be related to anthropogenic global warming, what we see is large annual and multidecadal variability, with the end of the record not looking much different than say a period around 1880 and with the highest GBI occurring in 1918 (with 1919 coming in 2nd place). While this doesn’t conclusively demonstrate that the current rise in GBI is not related to jet stream changes induced by sea ice loss, it most certainly does demonstrate that global-warming induced sea ice loss is not a requirement for blocking events to occur over Greenland and that recent events are not  at all “weird.”  An equally plausible, if not much more plausible, expectation of future behavior is that this GBI highstand is part of multidecadal natural variability and will soon relax back towards normal values.  But such an explanation isn’t Post-worthy.

Another big problem with all the new hype is that history shows the current goings-on in Greenland to be irrelevant, because humans just can’t make it warm enough up there to melt all that much ice. For example, in 2013, Dorthe Dahl-Jensen and her colleagues published a paper in Nature detailing the history of the ice in Northwest Greenland during the beginning of the last interglacial, which included a 6,000 year period in which her ice core data showed averaged a whopping 6⁰C warmer in summer than the 20th century average. Greenland only lost around 30% of its ice with a heat load of (6 X 6000) 36,000 degree-summers. The best humans could ever hope to do with greenhouse gases is—very liberally—about 5 degrees for 500 summers, or (5 X 500) 2,500 degree-summers. In other words, the best we can do is 500/6000 times 30%, or a 2.5% of the ice, resulting in a grand total of seven inches of sea level rise over 500 years. That’s pretty much the death of the Greenland disaster story, despite every lame press release and hyped “news” article on it.

While you won’t find this kind of analysis elsewhere, we’re happy to do it here at Cato. 


Dahl-Jensen, D., et al., 2013.  Eemian interglacial reconstructed from a Greenland folded ice core.  Nature 489, doi: 10.1038/nature11789.

Hanna, E., et al., 2016. Greenland Blocking Index 1851-2015: a regional climate change signal. International Journal of Climatology, doi: 10.1002/joc.4673.

Tedesco, M., et al., 2016. Arctic cut-off high drives the poleward shift of a new Greenland melting record. Nature Communications, DOI: 10.1038/ncomms11723, http://www.nature.com/ncomms/2016/160609/ncomms11723/full/ncomms11723.html

Release the Kraken

Global Science Report is a feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”

Making headlines today (like the one above) is a new paper by Zoë Doubleday and colleagues documenting an increase the population of cephalopods (octopuses, cuttlefish, and squid) over the past 61 years.  The authors, after assembling a data set of historical catch rates, note that this population increase, rather than being limited to a few localized areas, seems to be occurring globally.

End of analysis.

From then on its speculation.

And the authors speculate that human-caused climate change may be behind the robust cephalopod increase. After all, the authors reason, what else has had a consistent large-scale impact over the past six decades? No analysis relating temperature trends (spatially or temporally) to cephalopod trends, no examination of other patterns of climate change and cephalopod change, just speculation.  And a new global warming meme is born—“Swarms of octopus are taking over the oceans.”

There is an overwhelming tendency to relate global warming to all manner of bad things and a great hesitation to suggest a potential link when the outcome is seemingly beneficial. We refer to this as the global-warming-is-bad-for-good-and-good-for-bad phenomenon. It holds a great majority of the time.

In the case of octopuses, squids, and cuttlefish, the authors are a bit guarded as to their speculation of impact of the increase in cephalopod numbers—will they decimate their prey populations or will they themselves provide more prey to their predators? Apparently we’ll have to wait and see.

No doubt, the outcome will be a complex one as is the case behind the observed population increases. Depletion of fish stocks, a release of competitive pressure, and good old-fashioned natural environmental variability are also suggested as potential factors in the long-term population expansion. But complex situations don’t make for great scare stories. Global-warming-fueled bands of marauding octopuses and giant squid certainly do. 


Doubleday, Z. A., et al., 2016. Global proliferation of cephalopods. Current Biology, 26, R387–R407.

Arctic Sea Ice Loss Not Leading to Colder Winters

Global Science Report is a feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”

Although it’s a favorite headline as people shiver during the coldest parts of the winter, global warming is almost assuredly not behind your suffering (the “warming” part of global warming should have clued you in on this).

But, some folks steadfastly prefer the point of view that all bad weather is caused by climate change.

Consider White House Office of Science and Technology Policy (OSTP) head John Holdren. During the depth of the January 2014 cold outbreak (and the height of the misery) that made “polar vortex” a household name, OSTP released a video featuring Holdren telling us that “the kind of extreme cold being experienced by much of the United States as we speak, is a pattern that we can expect to see with increasing frequency as global warming continues.” 

At the time we said “not so fast,” pointing out that there were as many (if not more) findings in the scientific literature that suggested that either a) no relationship exists between global warming and the weather patterns giving rise to mid-latitude cold outbreaks, or b) the opposite is the case (global warming should lead to fewer and milder cold air outbreaks).

The Competitive Enterprise Institute even went as far as to request a formal correction from the White House. The White House responded by saying that the video represented only Holdren’s “personal opinion” and thus no correction was necessary. CEI filed a FOIA request, and after some hemming and hawing, the White House OSTP finally, after a half-hearted search, produced some documents. Unhappy with this outcome, CEI challenged the effort and just this past Monday, a federal court, questioning whether the OSTP acted in “good faith,” granted CEI’s request for discovery.

In the meantime, the scientific literature on this issue continues to accumulate. When a study finds a link between human-caused global warming and winter misery, it makes headlines somewhere. When it doesn’t, that somewhere is usually reduced to here.