Tag: Global Science Report

Tropical Cyclones: Is Global Warming Making Them Worse?

Severe hurricanes, or tropical cyclones as they are known by those living outside the United States, are the most intense storms on the planet. Given the amount of damage they can inflict, it’s no wonder that they often are the poster children for the global warming movement—think Hurricanes Andrew, Katrina, and Sandy. Whenever and wherever they occur, you can count on some climate lobbyist telling us that storm was caused, or made worse, by global warming. Indeed, it is a green legend that carbon-induced global warming will cause more frequent or more severe tropical cyclones in the future, resulting in escalating economic damages.

Is that really so? A new scientific study addresses this topic, by Dr. S. Niggol Seo of the prestigious University of Sydney. He examined trends in tropical cyclones affecting Australia and published his results in the academic journal Environmental and Resource Economics.

Writing as background for his work, Seo states that alarming predictions of more intense hurricanes because of climate change “are of great concern,” yet he says there have been “few TC [tropical cyclone] studies in the Southern Hemisphere,” adding that there has been “no economic assessment of damages in the past.” Based on detailed reports of TCs that were generated in the Southern Ocean and hit Australia since 1970, from the Australian Bureau of Meteorology, Seo constructed damage estimates “using the reported financial loss, destruction of houses and capital goods, and losses of agricultural crops and livestock after a careful examination of the detailed individual cyclone reports,” which also included “local area income and population density where the storm hit.” 

Seo’s examination of tropical cyclone data back to 1970 is important, because over that time (1970–2006) the carbon dioxide (CO2) concentration of the atmosphere rose by 55 parts per million (ppm), or more than half of global CO2 increase experienced since the dawn of the Industrial Revolution. In addition, global temperatures over this 36-year period rose by approximately 0.5°C,  to levels that some (controversially) consider unprecedented in the last two millenia. If there is a period of time in which one should be able to find a CO2/temperature-induced signal in the tropical cyclone record, the years examined by Seo would seem to be it. 

Despite this alignment of the stars, so to speak, Seo’s work fails to support claims that global warming is causing or will cause more frequent and severe tropical cyclones. 

U.S. Floods, Droughts and Global Warming: Another Wardrobe Failure

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.”

It is the current rage in the mainstream media and the government to tie almost everything into human-caused global warming—from a sluggish economy to Ebola,  and everything in between (and then some).

In fact, virtually none of these claims are supported by a consensus of evidentiary science. Here is (yet) another example, debunking the popular notion floods are being worsened by dreaded climate change caused by pernicious economic activity.

Clinically speaking, a “flood” is actually an extreme excursion in streamflow. So, if changes in streamflow are related to long-term changes in climate, and we accept that the majority of those latter changes are caused by said economic activity (we don’t), then our activities should increase streamflow and therefore the frequency of floods (or their opposite, droughts).

Two scientists from the U.S. Geological Survey (USGS), Gregory McCabe and David Wolock, recently examined historical (1951-2009) streamflow records from 516 rivers and streams that they considered to be only minimally impacted by human development. They first sorted the data into regional patterns, and then compared the temporal behavior of these patterns to  common historical climate indices—such as well-known patterns of atmospheric circulation, sea surface temperatures, or even large-scale warming.

It turns out that there weren’t any relationships between streamflow and the larger atmospheric phenomena.  Or at least, so very few that they are hardly worth mentioning.

Here is how McCabe and Wolock describe what they (didn’t) find:

Comparing time series of climate indices…with the time series of mean [stream] flow for the 14 clusters [patterns] indicates weak correlations that are statistically significant for only a few clusters. These results indicate that most of the temporal variability in streamflow in the conterminous U.S. is unpredictable in terms of relations to well-known climate indices. [emphasis added]

In other words, trends and/or variability in larger-scale features of the climate (including rising temperature from global warming) are not very strongly (if at all) related to regional and temporal characteristics of streamflows across the U.S.

And before anyone starts to argue that we have left out the direct (i.e., local) effect of global warming—that warmer air holds more moisture and thus it can rain more frequently and harder—McCabe and Wolock report very few long-term trends that would be indicative of steadily rising moisture levels. Instead, the find the historical records dominated by periods of multidecadal variability. In their own words:

Analyses of the annual mean streamflow time series for the 14 streamflow clusters indicated periods of extended wet and dry periods, but did not indicate any strong monotonic trends. Thus, the mean cluster streamflow time series indicate nearly random variability with some periods of persistence.

The bottom line is that McCabe and Wolock do not identify any behavior in historical U.S. streamflow records that is suggestive of an influence from human-caused global warming.

So next time you hear that there are increasing droughts or floods in the U.S. and that they are, through some convoluted explanation, “consistent with” global warming, remember two things: 1) “consistent with” is not the same as “caused by” and, 2) the consensus science linking global warming to changing streamflow characteristics across the U.S. is lacking.

Reference:

McCabe, G. J., and D. M. Wolock, 2014. Spatial and Temporal Patterns in Conterminous United States Streamflow Characteristics. Geophysical Research Letters, doi:10.1002/2014GL061980

 

Backyard Birds Spreading as Climate Changes

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.”

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In a recent Global Science Report, we posted some good news coming out of California’s Sierra Nevada, where climate change (from whatever cause), has been partially responsible for a greening of the organo state. Technically, the biomass in the montane forests has been on the increase over the past several decades.

Turns out climate change is for the birds, too. Yes, little Eastern Bluebirds (which almost went extinct because of habitat damage)—raising their young in cute houses, awakening us with their melodious songs, providing free cat food, and selectively messing only on my car. What’s not to like? And who wouldn’t like more birds? And if you live in the Eastern United States, there is a climate-related increase in cat purring because global (actually, local/regional) warming is increasing the range of songbirds.

A new study appearing in the journal Global Change Biology, authored by Karine Princé and Benjamin Zuckerberg from the University of Wisconsin-Madison’s Department of Forest and Wildlife Ecology, finds that:

[A] shifting winter climate has provided an opportunity for smaller, southerly distributed species to colonize new regions and promote the formation of unique winter bird assemblages throughout eastern North America.

The operative word here is “colonize.” In other words, they are spreading out from their home range, not moving north in lockstep.

California Greening

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.”

With all of the negative effects predicted to occur in response to the ongoing rise in the air’s carbon dioxide (CO2) concentration—a result of burning fossil fuels to produce energy—it is only natural to want to see what has been happening to our Earth’s many ecosystems as the atmospheric carbon dioxide load has risen. (Its atmospheric concentration has risen from around 280 parts per million to nearly 400 ppm, an increase of about 43 percent).

A new study by the University of California’s Christopher Dolanc and colleagues does just that, for the diverse Sierra Nevada forests of California. 

Dolanc and his colleagues analyzed two periods: historic measurements between 1929 and 1936, and modern data from 2001 through 2010.  And when we said “diverse,” we meant it.  They “classified 4,321 historical plots and 1,000 modern plots into nine broad groups of vegetation types that are widely used by land managers and researchers in the region.” This is what grad students are for!

They compared tree density and composition between the two periods, within and between the nine types of forest. The results shown in Figure 1 below.

 

Figure 1. Percent change in tree density by forest type in the Sierra Nevada Range, USA, as determined from historic (1929-1936) and modern (2001-2010) measurements. Green bars denote a statistically significant change. You might want to call this “California Greening.” Source: Dolanc et al. (2014).

Explosive Findings on Volcanoes’ Climate Influence

Global Science Report is a weekly 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 overturns old suppositions regarding volcanoes, tree-rings, and climate sensitivity.

According to a 2012 press release accompanying a paper published in the journal Nature Geoscience, a research team led by Penn State’s Dr. Michael Mann concluded that the cooling influence of historical volcanic eruptions was underrepresented by tree-ring reconstructions of the earth’s temperature.

This, the press release went on to tell us, had potential implications when trying to determine the earth’s equilibrium climate sensitivity (ECS)—i.e., how much the global average surface temperature will rise as a result of a doubling of the atmosphere’s pre-industrial concentration of carbon dioxide. While most recent studies place the ECS noticeably less than earlier studies (including those most heavily relied upon by the U.N.’s Intergovernmental Panel on Climate Change (IPCC) and thus the U.S. Obama Administration), the 2012 Mann study was an exception. It implied that many existing determinations of the ESC were underestimates.

From the press release:

“Scientists look at the past response of the climate to natural factors like volcanoes to better understand how sensitive Earth’s climate might be to the human impact of increasing greenhouse gas concentrations,” said Mann. “Our findings suggest that past studies using tree-ring data to infer this sensitivity have likely underestimated it.”

Fast forward to today.

Appearing on-line in the journal Geophysical Research Letters (and sans press release) is a paper led by Penn State’s Martin Tingley that examined how the temperature response from volcanic inferred from tree-rings compared with that of observations. Tingley’s team concluded that tree-ring based temperature proxies overestimated the temperature response caused by large volcanic eruptions. Instead of responding only to the cooler temperatures, the tree rings also included signals from reduced light availability (from the shading effect of volcanic aerosols) and the two effects together produced a signal greater than what would have been produced by cooler temperatures alone. This is basically the opposite of what Mann and colleagues concluded.

New Research Erases Global Warming from Pacific Northwest

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.”

Poof, it was gone.

Just like that, the human fingerprints on a century-long warming trend in Northwestern United States were erased and replaced instead by the telltale signs of natural variability. 

That is the conclusion of new research published last week by a pair of scientists from the University of Washington. James Johnstone and Nathan Mantua published their paper titled “Atmospheric controls on northeast Pacific temperature variability and change 1900-2012” in the Proceeding of the National Academy of Sciences (PNAS).

So as not to be accused of putting words in their mouth, here, in full, are the contents of a box labeled “Significance” from their paper:

Northeast Pacific coastal warming since 1900 is often ascribed to anthropogenic greenhouse forcing, whereas multidecadal temperature changes are widely interpreted in the framework of the Pacific Decadal Oscillation (PDO), which responds to regional atmospheric dynamics. This study uses several independent data sources to demonstrate that century-long warming around the northeast Pacific margins, like multidecadal variability, can be primarily attributed to changes in atmospheric circulation. It presents a significant reinterpretation of the region’s recent climate change origins, showing that atmospheric conditions have changed substantially over the last century, that these changes are not likely related to historical anthropogenic and natural radiative forcing, and that dynamical mechanisms of interannual and multidecadal temperature variability can also apply to observed century-long trends.

 

Translation: Natural variability in the atmosphere/ocean dynamics of the northern Pacific Ocean rather than human-caused global warming can largely explain the century-long rise in temperature in the Pacific Northwest.

And the authors have the figures to prove it.

The Collection of Evidence for a Low Climate Sensitivity Continues to Grow

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.”

Nic Lewis and Judith Curry just published a blockbuster paper that pegs the earth’s equilibrium climate sensitivity—how much the earth’s average surface temperature is expected to rise in association with a doubling of the atmosphere’s carbon dioxide concentration—at 1.64°C (1.05°C to 4.05°C, 90% range), a value that is nearly half of the number underpinning all of President Obama’s executive actions under his Climate Action Plan.

This finding will not stop the President and the EPA from imposing more limits on greenhouse-gas emissions from fossil fuels. A wealth of similar findings have appeared in the scientific literature beginning in 2011 (see below) and they, too, have failed to dissuade him from his legacy mission.

The publication of the Lewis and Curry paper, along with another by Ragnhild Skeie and colleagues, brings the number of recent low-sensitivity climate publications to 14, by 42 authors from around the world (this doesn’t count our 2002 paper on the topic, “Revised 21st Century Temperature Projections”).  Most of these sensitivities are a good 40% below the average climate sensitivity of the models used by the U.N.’s Intergovernmental Panel on Climate Change (IPCC).

Lewis and Curry arrive at their lower equilibrium climate sensitivity estimate by using updated compilations of the earth’s observed temperature change, oceanic heat uptake, and the magnitude of human emissions, some of which should cause warming (e.g., greenhouse gases), while the others should cool (e.g., sulfate aerosols). They try to factor out “natural variability.” By comparing values of these parameters from the mid-19 century to now, they can estimate how much the earth warmed in association with human greenhouse gas emissions.

The estimate is not perfect, as there are plenty of uncertainties, some of which may never be completely resolved. But, nevertheless, Lewis and Curry have generated  a very robust observation-based estimate of the equilibrium climate sensitivity.

For those interested in the technical details, and a much more thorough description of the research, author Nic Lewis takes you through the paper (here) has made a pre-print copy of the paper freely available (here).

In the chart below, we’ve added the primary findings of Lewis and Curry as well as those of Skeie et al. to the collection of 12 other low-sensitivity papers published since 2010 that conclude that the best estimate for the earth’s climate sensitivity lies below the IPCC estimates. We’ve also included in our Figure both the IPCC’s  subjective and model-based characteristics of the equilibrium climate sensitivity. For those wondering, there are very few recent papers arguing that the IPCC estimates are too low, and they all have to contend with the fact that, according to new Cato scholar Ross McKitrick, “the pause” in warming is actually 19 years in length. 

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