Tag: Global Science Report

California Irrigation Supplies Water to Phoenix

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.”

California’s Central Valley is one of the true wonders of the agricultural world.  Prior to settlement, it was grassland in its northerly regions (around Sacramento) and desert at the southern end (Bakersfield).  As a result of irrigation from water stored both in the ground and in the many rivers that drain into it, this 1 percent of the nation’s cropland produces 8 percent of our national agricultural output (by value). That doesn’t count the equally productive but much smaller Salinas Valley, which is likely where your artichokes came from.

John Christy, a fellow-lukewarmer (and a Valley native) who is also state climatologist for Alabama, has published extensively that irrigation has changed the Valley’s climate, resulting in a warming produced not by carbon dioxide but by water vapor, which tends to skew heating into the night.

Everything else being equal, increasing the surface moisture in a hot-as-heck environment (like the Central Valley) will increase atmospheric instability, and, given proper conditions, should result in increased convective (thunderstorm) activity. Add in that prevailing mid-atmospheric winds in this region blow from west to east, and you wind up running the increased water vapor uphill into the Sierras, the Wasatch, and the Rockies. That’s pretty much guaranteed to increase thunderstorm activity.

A newly published study fleshes this out with a computer model, and finds that irrigation in the Central Valley of California not only adds water to the local environment but also alters the regional climate across the Colorado River Basin, increasing summer precipitation by 15 percent and Colorado River flow by nearly 30 percent. Those are big numbers and important ones, given the water needs of some 35 million people from Las Vegas to Phoenix to L.A.

Two Wrongs Don’t Make a Right

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.”

As economic heavyweights assembled for their annual summit held by the World Economic Forum (WEF) in Davos, Switzerland, they were greeted by a call for $700 billion/yr of increased spending out to the year 2030 to “to close the green investment gap worldwide, leading to sustainable economic growth that attains global climate change goals.” They were told that this goal can be reached through an additional $36 billion/yr investment from the world’s governments (on top of the $96 billion/yr currently spent) that will “spur up to US$ 570 billion in private capital needed to avoid devastating climate impacts on economy.”

This call was made by the WEF’s own Green Growth Action Alliance as it released its first Green Investment Report at the outset of the Davos conference.

The Green Growth Action Alliance justified the call for the extra spending this way:

Such investments are urgently needed to avoid the potentially devastating impacts of climate change and extreme weather events as witnessed in many parts of the world in 2012. Scientists agree that extreme weather has become the “new norm” and comes at a huge, and rising, cost to the global economic system. Without further action, the world could see a rise in average global temperatures by 4ºC by the end of the century. According to scientists, this could lead to further devastating impacts, including extreme heat waves, more intense tropical storms, declining global food stocks and a sea-level rise affecting hundreds of millions of people.

Using a poor excuse to call for a bad idea doesn’t seem much like progress.

The science of global warming re extreme events is hardly compelling.  The data noise, generated from both natural processes and from other human influences, largely overwhelms any anthropogenic greenhouse effect signal in most cases.

However, compelling evidence is emerging that the magnitude of the climate sensitivity—that is, how much warming we should expect from a doubling of atmospheric carbon dioxide concentration—has been overestimated. Even if there was good scientific evidence that higher temperatures lead to a more “extreme” climate (there’s just about as much evidence for the opposite), an overestimate of the sensitivity would lead to an overestimate of extremes.

And these overestimates are being used by the Green Growth Action Alliance to oversell the need to do something about climate change.

In fact, there are much more pressing needs.

New Government Climate Change Report Yet More “Show Science”

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.”

You can get anything you want

At Alice’s Restaurant

-Arlo Guthrie, 1967

Late last week, the U.S. Global Climate Change Research Program (USGCRP) released a draft version of its latest assessment report on the impacts of climate change in the United States. Updated reports are required by Congressional decree every 4 years or so.  The 2013 report, as it now stands, tips the scales at over 1,000 pages, consequently, we haven’t made our way through it yet, but if the Executive Summary is any indication, this report seems even worse than the one the USGCRP released in 2009.

This is yet another example of our imperial government’s predilection towards “show science” in order to justify taking people’s stuff.  By analogy, think of the “show trials” in some of history’s more freedom-loving regimes. 

As of this writing, it’s not clear if they intend to produce another “summary” document, such as the 200-pager they put out in 2009. That one was so bad as to require us to produce an Addendum that represents what the USGCRP report coudda, shoudda, woudda looked like had the author team made a more complete and fair assessment of the scientific literature.

Admittedly, our Addendum report, which was finalized and released last fall, did include citations from the scientific literature that were published subsequent to the publication of the 2009 USGCRP report, which obviously the USGCRP report authors couldn’t have known about.  But, as our Addendum demonstrates, when these new research results are included, the potential impacts of climate change in the U.S. are substantially tempered.  This leads us to think that the 2013 version from the USGCRP—which seems to hype the impacts of anthropogenic greenhouse gas emissions even more so than the 2009 report did—didn’t do a grand job  in synthesizing the literature.

Nor does it appear they did a good job with the statistics of climate and climate change in the U.S.

Another Lower Climate Sensitivity Estimate

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.”

As the earth’s climate sensitivity is perhaps the key factor in what climate lies ahead, we’ll often report on scientific findings that enhance our understanding of this important parameter.

Recall from our previous discussion, that the earth’s “climate sensitivity” is the amount that the average global surface temperature will rise, given a doubling of the concentration of atmospheric carbon dioxide (CO2) from its pre-industrial value. This metric is the key to understanding how much global warming will occur as we continue to burn fossil fuels for energy and emit the resultant CO2 into the atmosphere.

And as we mentioned, the big problem is that scientists don’t know what the true value of the climate sensitivity really is. The U.N.’s Intergovernmental Panel on Climate Change (IPCC) summed up its assessment of the science regarding the value of the climate sensitivity in its 2007 Fourth Assessment Report (AR4) thusly:

It is likely to be in the range 2°C to 4.5°C with a best estimate of about 3.0°C, and is very unlikely to be less than 1.5°C. Values substantially higher than 4.5°C cannot be excluded…

New findings seem to be coming in with some regularity since the publication of the AR4 that the IPCC’s estimate is on the high side of reality.  We discussed some of these findings in our publication Addendum: Global Climate Change Impacts in the United States (p.26-27) and more recent ones in a Global Science Report last month.

Now we have another new, lower estimate, to report on.

Warmest Year on Record in the U.S.

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.”

When the book closes on the year 2012, it will go down as the warmest year in the National Climatic Data Center’s  (NCDC) history for the contiguous U.S.—a history that goes back to 1895.

And quite a warm year it was, topping the old record held by 1998 by about 1°F—a sizeable margin of victory. In the chart below (Figure 1), I have plotted the entire 118 year record, including the overall average (solid red line) and the 95% confidence range about that mean (+/- two times the detrended standard deviation; dotted red lines). I have also included the linear trend over the 118 years—a value of 0.13°F/decade.

 

Figure 1. U.S. annual average temperatures, 1895-2012 (data source NCDC, 2012 estimated).
 

Notice that the linear is not a great measure of what has been going on climatologically. There have been several multi-decadal periods when the average U.S. temperature has been generally above (1920s-1930s; mid-1990s-present) or below (1890s-1910s; 1960s-1970s) the linear trend term—an indication that larger-scale (quasi-cyclical?) variability plays a defining role in the character of the temperature history.

The role that anthropogenic “global warming” from the emissions of greenhouse gases from the combustion of fossil fuels plays is debatable—both in timing and magnitude. Almost certainly its influence is present and detectable in the U.S. annual average temperature record, but beyond that simple statement, not a whole lot more can be added with scientific certainty.

Shown below (Figure 2) is the relationship between mean annual global temperature departures from the long-term average and U.S. temperature anomalies.  Statistically, the correspondence between the two is 35%, which means that there are a lot of other things influencing our temperature.

 

Figure 2. Relationship between global and U.S. annual average temperature anomalies, 1895-2011 (data source: NCDC).
 

 

Further, as I have pointed out, there is little we could do to alter the climate influence of anthropogenic emissions even if we wanted to.  So, probably the best thing to do when planning for the future is to be aware of the more or less capricious nature of our nation’s climate and keep in mind that humans are supplying an ever-growing warming pressure on top of that. The Boys Scouts got at least one thing right.

CO2 Benefits Outweigh Climate Stressors: Chinese Wheat

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.”

In the vast majority of laboratory and field experiments, the benefits of higher atmospheric carbon dioxide (CO2) concentrations for plants (including food crops) generally outweigh the negative impacts from climate change. And this is even assuming the “dumb farmer scenario” that we recently blogged, in which farmers and agronomists don’t develop new production techniques, technologies, crop varietals, etc., to adapt to change, turning expected losses into gains. There is overwhelming evidence such as the remarkably robust increase that has occurred in the yield of most of the world’s major crops when grown in developing or developed nations. In other words, adding CO2 to the atmosphere may be a win-win situation for the world’s vegetation, but we digress…

Here, we’ll highlight a new study showing that including the fertilization effect of higher CO2 concentrations in a crop model of wheat grown in China turns projections of future climate change-driven reductions in crop yields into CO2-driven yield increases.

The study was conducted by researchers Yujie Liu and Fulu Tao of the Chinese Academy of Sciences and will soon be published in the Journal of Applied Meteorology and Climatology. Liu and Tao used a complex crop model to evaluate the changes in wheat production (which accounts from 22% China’s primary food production), in the main wheat cultivation areas in China under three climate change scenarios—global temperature increases of 1°, 2°, and 3°C. They modeled the crop response both with and without considering the fertilization impacts of additional atmospheric CO2 concentrations (which presumably produced the warming) and compared the results. Here is their summary:

There is a high probability of decreasing (increasing) changes in yield and water use efficiency under higher temperature scenarios without (with) consideration of CO2  fertilization effects. Elevated CO2 concentration generally compensates for the negative effects of warming temperatures on production. Moreover, positive effects of elevated CO2 concentration on grain yield increase with warming temperatures. The findings could be critical for climate change-driven agricultural production that ensures global food security.

Findings and conclusions like these are a breath of carbon dioxide-enhanced fresh air in a world of climate gloomsaying.

Reference:

Liu, Y., and F. Tao, 2012. Probabilistic change of wheat productivity and water use in China for global mean temperature changes of 1, 2, and 3°C. Journal of Applied Meteorology and Climatology, doi:10.1175/JAMC-D-12-039.1, in press.

The Latest Greenland Kerfluffle: If Their Science Can’t Be Refuted, Smear ‘Em

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.”

About a year and a half ago, we were co-authors (along with Dr. Oliver Frauenfeld from Texas A&M University) on a paper published in the Journal of Geophysical Research in which we presented a nearly 225-year reconstruction of surface snow melt across Greenland (Figure 1).

Our reconstruction was based on long-term temperature records from the southern Greenland coast along with historic indicators of the atmospheric circulation in the North Atlantic Ocean. We found that in addition to the period since about the year 2000, there was an extended (multi-decadal) period in the early portion of the 20th century where the amount of surface snowmelt was elevated above the long-term average.  We concluded from this that since there did not appear to be a large increase in the rate of global sea level rise during the early 20th century period of elevated ice melt—a melt driven primarily by warmer than normal temperatures—that Greenland’s contribution to global sea level rise during the current period of high temperatures was likely to remain relatively “modest,” at least for the next few decades.

Figure 1. Reconstructed history of the total ice melt extent index over Greenland, 1784–2009. Observed values of the ice melt index (blue solid circles), reconstructed values of the ice melt index (gray open circles), the 10 year trailing moving average through the reconstructed and fitted values (thick red line), and the 95% upper and lower confidence bounds (thin gray lines) (from Frauenfeld et al., 2011).

Neither our methods, nor or findings were overly controversial—or so we thought.

Shortly after our paper was published, one of the reviewers of our paper, a noted snow/ice researcher who has spent a lot of time studying Greenland, Dr. Jason Box, came forwarded and denounced our work. On his blog (in posts he has subsequently removed), he attacked our work both from a scientific standpoint as well as deriding it with a few ad hominems (for example “Examining the 2nd [Knappenberger] and 3rd [Michaels] authors’ credentials, a climate change denialist pattern emerges”).

On both accounts we felt he was wrong (of course) and offered a rebuttal.

But perhaps the strongest argument that our results were scientifically sound comes from an ironic source—the results of new research findings from Jason Box himself!

These new findings from Box, although not yet fully available, have been incorporated into another research project that has recently been published (Gregory et al., 2012) and thus we can get a sneak peek at them.

The solid black line in Figure 2 (below) shows Box’s reconstruction of the sea level rise contribution from Greenland back into since the mid-1800s.

Figure 2. Various estimates of the time series of the Greenland ice-sheet mass contribution to global-mean sea-level rise. The reconstructions are plotted as ten-year running time-means of the sea-level equivalent of the rate of change of mass of the Greenland ice-sheet with respect to the mean of 1961–1990. The solid black line, labeled “B” is the net mass balance, including both surface mass balance and ice discharge from Jason Box. The horizontal dotted line indicates zero. The vertical lines indicate the years in which major volcanic eruptions occurred (from Gregory et al., 2012).

Notice the strong resemblance of Box’s reconstruction of the sea level contribution from Greenland with our reconstruction of the surface snow melt across Greenland.  The snow melt/sea level contribution is currently very high, was relatively low in the 1970s, 1980s, and 1990s, was high from the mid-1920s through the late 1960s, and was lower in the 1800s.

Considering that there are other factors besides snowmelt (like snow accumulation and calving glaciers) that contribute to Greenland’s net contributions to sea level rise, the two curves are remarkably similar. This is a strong indication that whatever is driving snowmelt (regional temperature) is also driving the net sea level contribution.

All of which we wrote in our paper:

This record of ice melt indicates that the melt extent observed since the late 1990s is among the highest likely to have occurred since the late 18th century, although recent values are not statistically different from those common during the period 1923–1961, a period when summer temperatures along the southern coast of Greenland were similarly high as those experienced in recent years. Our reconstruction indicates that if the current trend toward increasing melt extent continues, total melt across the Greenland ice sheet will exceed historic values of the past two and a quarter centuries

…The forces acting in concert with ice melt across Greenland to produce higher global sea levels currently, should also have been acting during the extended high‐melt conditions from the mid‐1920s to the early 1960s.

And we also added this concerning the significance of Greenland’s contribution to the total global sea level rise:

[T]here is no indication that the increased contribution from the Greenland melt in the early to mid 20th century, a roughly 40 year interval when average annual melt was more or less equivalent to the average of the most recent 10 years (2000–2009), resulted in a rate of global sea level rise that exceeded ~mm/yr.  This suggests that Greenland’s contribution to global sea level rise, even during multidecadal conditions as warm as during the past several years, is relatively modest.

Figure 3 (anther figure from the new paper from Gregory et al., 2012) shows the breakdown of the factors contributing to the global rise in sea level of the past century and a half.  Greenland’s contribution (based on Box’s reconstruction) is the pale green line (labeled “Greenland-B” in the legend). I think it is pretty fair to characterize this as “modest.”

Figure 3. Observational (black) and a reconstructed (red) time series of global mean sea-level rise (thick lines, with 5–95% observational uncertainty shaded), also showing the contributions to the latter (thin lines), identified by the time series initials in the key (from Gregory et al., 2012).

Why was such a big deal was made about our research results and “denialist” credentials when subsequent results, made by the very person who went ad hominem, completely replicate our findings?

References:

Box, J. E., Greenland ice sheet mass balance reconstruction. Part III: Marine ice loss and total mass balance (1840–2010). Journal of Climate, submitted (as cited by Gregory et al., 2012).

Frauenfeld, O.W., P.C. Knappenberger, and P.J. Michaels, 2011. A reconstruction of annual Greenland ice melt extent, 1785-2009. Journal of Geophysical Research, 116, D08104, doi: 10.1029/2010JD014918.

Gregory, J., et al., 2012. Twentieth-century global-mean sea-level rise: is the whole greater than the sum of the parts? Journal of Climate, doi:10.1175/JCLI-D-12-00319.1, in press.