Arguments
A tale told in maps and charts: Texas in the National Climate Assessment
Posted on 26 July 2013 by dana1981
This is a partial re-post from Texas Climate News
Off the chart: The new National Climate Assessment contains numerous references to Texas' record-setting heat and drought in 2011. Those harsh conditions – the large red dot on this chart – "represent conditions far outside those that have been registered since the instrumental record began" in the 19th century, the report says. "Generally," it adds, "the changes in climate are increasing the likelihood for these types of severe events."
By Bill Dawson
Texas Climate News
Expert authors: 240. Number of pages: 1,146.
Those two numbers convey a sense of the scope of the scientific effort that went into a new federally-comissioned report on climate change, issued last month in draft form. The study “collects, integrates, and assesses observations and research from around the country, helping to show what is actually happening and what it means for peoples’ lives, livelihoods, and future.”
The first paragraph of the National Climate Assessment – the first updated edition of that congressionally-ordered study in four years – conveys a sense of its sweeping findings:
Climate change is already affecting the American people. Certain types of weather events have become more frequent and/or intense, including heat waves, heavy downpours, and, in some regions, floods and droughts. Sea level is rising, oceans are becoming more acidic, and glaciers and arctic sea ice are melting. These changes are part of the pattern of global climate change, which is primarily driven by human activity.
Katharine Hayhoe, director of the Climate Science Center at Texas Tech University and a lead author of one chapter in the report, told the Associated Press: “There is so much that is already happening today. This is no longer a future issue. It’s an issue that is staring us in the face today.”
And it will continue to do so in coming years and decades, the report stresses:
Human-induced climate change is projected to continue and accelerate significantly if emissions of heat-trapping gases continue to increase. … Climate change threatens human health and well-being in many ways, including impacts from increased extreme weather events, wildfire, decreased air quality, diseases transmitted by insects, food, and water, and threats to mental health.
What does – and will – it mean for Texas? The report has no single, comprehensive, state-level appraisal, per se, but one way to get a general idea of what it says on that question is to glean it from maps and other graphics that illustrate many of the key conclusions and projections included by the authors.
TCN reviewed the report’s 1,146 pages to assemble this selection of graphics with Texas-related information. (Captions beneath the graphics reproduced below also appear in the report.)
+++ Temperature +++
U.S. temperature change: 1991-2011 vs. 1901-1960
Most of Texas has been growing warmer over the past two decades – less so than many parts of the country, but more than some Southeastern states.
Temperature projection: 2070-2099
In the 2070-2099 period, compared to 1971-1999, average surface air temperatures in Texas are projected to be 3 to 5 degrees F warmer if there are “substantial reductions in heat trapping gases” and 6 to 9 degrees F warmer in a higher-emission scenario.
More AC-conducive days
Texans use a lot of air conditioning already. A study projected a considerably greater increase in the state in “cooling degree days” (when people tend to use air conditioning) with higher emissions of greenhouse gases.
+++ Drought and water +++
Drought severity
Droughts would grow more damaging in Texas under this 2011 projection, though not by as much as in parts of Mexico and in areas of the U.S. to the north and northwest of the state. Lower numbers on the standard Palmer Drought Severity Index indicate drier conditions.
“Dry days”
In a contrast with Plains states to the north, Texas is projected to experience more “dry days” – those with less than a tenth of an inch of precipitation – more so if greenhouse emissions continue to rise (map at right) than in a scenario with “substantial reductions.”
For more, click here to re-direct to the full Texas Climate News post
I have problem understaqnding the nomenclature of some figures.
Figure 4.3 introduces "Cooling Degree Days" on the scale from 0 to 2800. What does it mean that CDD==2800? Per year is impossible, so maybe per decade or per the entire period shown?
On the other hand, Figure 19.3 shown delta of "Number of Dry Days" on the scale from -8 to +6. Again, what does this measure mean? What was the base of that delta? Per year, per decade or per entire period like in the previous example?
I cannot have a "feeling" as to the magnitude of those changes because the measures is so poorly defined that you don't really know what numbers they show.
Is it only me having problems here ? Maybe someone else who understands the undefrlying research can explain the nukmbers to me...
I wonder if, in time, this heatwave in Texas will be put down primarily to natural variability as was the Russian heatwave in 2010 (Dole et al Geophysical Research Letters 2011) and the hot US summer of 2012 (Dole et al Bulletin of the American Meteorological Society 2013). It is fascinating to see the changes in opinion that the passing of time brings. For example Skeptical Science in 2012 ran this piece by Rob Painting
"An American Heatwave: The United States Glimpses its Hot Future" As indicated by the title the implication was that AGW rather than natural variability could be the causative culprit. That said, it is necessary to note that the 2010 paper by Dole was very fairly critiqued by Rob Painting. It still seems uncertain whether AGW or natural varability is the primary cause of extreme weather events but to discount either at this stage may be premature
chriskoz, from Wikipedia a CDD seems to be approximately each one degree of external temperature above that which would maintain an internal temperature at a preditermined baseline (commonly 60°F or 65°F) without energy being expended on cooling. Wikipedia explains it in terms of degrees C, but I'm sure Texas' data would be in F°. The current annual average for Houston, according to ClimateZone.com, is 2700 CDD, so it appears that 2800 CDD would be an annual average also. I found some more accurate formulae for calculating degree days at http://www.vesma.com/ddd/ddcalcs.htm
Good point Ray (#2). However one does need to be careful in assessing these very-difficult-to-attribute events especially based on single studies.
For example Rahmstorf, S., and D. Coumou (2011) Increase of extreme events in a
warming world, Proc. Natl. Acad. Sci. U. S. A., 108(44), 17905–17909 concluded that background global warming in Western Russia has increased the probability of extreme warming events by around 5-fold and explicitly contridict the conclusions of the Dole paper you cite in terms of the predictability of the event.
Otto et al (2012) Reconciling two approaches to attribution of the 2010 Russian heat wave Geophys. Res. Lett., VOL. 39, L04702,doi:10.1029/2011GL050422, 2012, suggest that the two studies (Dole and Rahmstorf) are not necessarily in contradiction in that "the same event can be both mostly internally-generated in terms of magnitude and mostly externally-driven in terms of occurrence-probability" (easier to quote than to paraphrase!).
In other words global warming increases the probability of extreme warming events (this isn't controversial I think) such that we expect a greater probability of extreme weather (esp warming), even if a detailed local attribution gives the appearance of largely natural inputs.
It's worth noting that even 'though the Dole paper you cite indicates that natural variability doinates local inputs for the Moscow heatwave in their analysis ('though contradicted by the Rahmstorf study), Dole et al do warn that:
"Nevertheless,there is evidence that such warming has contributed too observed heat waves in other regions, and is very likely to produce more frequent and extreme heat waves later this century [Intergovernmental Panel on Climate Change, 2007]. To assess this possibility for the region of western Russia, we have used the same IPCC model simulations to estimate the probability of exceeding various July temperature thresholds over the period 1880–2100 (Figure 4). The results suggest that we may be on the cusp of a period in which the probability of such events increases rapidly, due primarily to the influence of projected increases in greenhouse gas concentrations."
I'm curious how much long term inertia is in the system. In other words, even if we held CO2 levels to 400ppm, what climate would we end up with when all the interlocking feed back mechanisms have worked their way through the system. Of course, in the mean time, we are heading at a little below 3ppm per year towards 500ppm. It's quite exciting if you are in to horror movies. When will we first see CO2 levels start to rise more quickly than we would expect from the level of our emissions.
@william #5 Dr. James Hansen says his best estimate with feedbacks for CO2 doubling is +2.8 Celsius (climate sensitivity) and Dr. Davis Randall says +2.4C. 400ppm is 52% of CO2 doubling assuming steady feedbacks, so that's +1.3 to +1.5C. I recall somebody (maybe Dr. Kevin Trenberth) saying "another 0.5 degrees in the pipeline" so that fits with +1.4C if it is +0.9C now (I keep forgetting the base times). Apparently, +1.4C is a reasonable projection. The oceans are ~1,000 years behind land and air because of their mixing rates so it would generally stay somewhat below +1.4C for ~1,000 years, likely with little fits and starts like we've already seen because of variation in ocean mixing.
@Me#6 typo: Dr. David Randall.
Ray,
Hansen (summarized here) has estimated from data that approximately 98% of heat waves have been caused by AGW. While there is still scientific discussion about the exact proportion of heat waves caused by AGW, your "primarily to natural variability as was the Russian heatwave in 2010" is certainly not a consensus statement. While Hansen's data applies to hot summers and shorter heat waves like Russia's are not directly applicable, it seems reasonable that if 98% of hot summers are caused by AGW, most short term heat waves are also due to AGW. AIR, Ramsdorf estimated an 80% chance that the Russian heat wave was caused by AGW, hardly "primarily natural variability". This is an area of active research. I note that in the past scientists have been conservative in their estimates. It will be interesting to see the conclusions in the next IPCC report.
Grindup: you have not counted the cooling caused by aerosols in your calculation. When coal use declines, the aerosol cooling effect will decrease. The exact cooling caused by aerosols is poorly estimated, but is likely around .5C. That needs to be added to the heat in the pipeline.