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2014 US National Climate Assessment Released

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The US Global Change Research Program issued its latest National Climate Assessment today. There are lots of goodies in it.  I want to focus on a couple of things that caught my eye in an initial skim.

Impacts will increase in frequency and severity (no big surprise there). This assessment includes up-t0-date research results on those impacts.  Like most reports, they leave `Responses` as a final category.  I understand the logic of laying out the evidence of climate change and its impacts prior to discussing solutions, but as I’ve written before today, people primarily respond to solutions and not problems.  Only the most dedicated readers will make it all the way through the report to get to the Response section.  My worry is that the Response section will not be the focus of activists’ attention; a continuation of decades of wasted energy.

Extreme Weather

The report summarizes the state-of-the-science well: “Over the last 50 years, much of the U.S. has seen increases in prolonged periods of excessively high temperatures, heavy downpours, and in some regions, severe floods and droughts.”  That is accurate.  I do not think one example is valid, however.  The report discusses anomalous warmth and dryness in Texas and Oklahoma in 2011.  I do not argue that the event occurred; I blogged about it and the subsequent 2012 Great Plains drought.  Where I deviate from the Assessment is this: there is scant evidence that the 2011 Southern Plains drought had a strong climate signal.  The same goes for the 2012 Great Plains drought.  Instead, these droughts were strongly linked to drier summertime conditions during the recent decade as part of a regime shift, most probably due to natural decadal variability (Hoerling et al. 2014).  The 2011 Texas heat wave was more likely to occur than it was 40 years ago.  This is not the same thing as identifying a clear attribution – something that remains at the cutting edge of climate science.

Likewise, the largest determinant of Atlantic hurricanes remains natural variability.  The Assessment’s statement that Atlantic hurricane activity increased since the early 1980s is true, but there are important details to consider.  The Atlantic signal is opposite the global signal (a small reduction in overall hurricane activity in that same time period), so regional effects are important to consider.  The Atlantic Multidecadal Oscillation is currently in a positive phase (since the early 1980s – isn’t that interesting?), which includes a warmer than usual Atlantic Ocean.  All else equal, this facilitates tropical storm development, which we’ve seen.

The Assessment’s conclusion stands in direct contrast to a couple of peer-reviewed papers, including Chylek and Lesins 2008 (we find no increase in the number of major hurricanes (category 3–5); If there is an increase in hurricane activity connected to a greenhouse gas induced global warming, it is currently obscured by the 60 year quasi-periodic cycle.) and Enfield and Cid-Serrano 2009 (Projections to the year 2025 show that the cumulative change in summer warm pool size since 1975 will depend critically on whether a subsequent cooling in the multidecadal cycle occurs, comparable to the warming between 1975 and 2000 AD.)  In other words, determining how man-made warming affects Atlantic hurricanes will not be detectable from the natural signal for many years to come.

That doesn’t mean we do nothing.  To the contrary, I argue that we need to adapt our current infrastructure to our current climate.  Multi-billion dollar events occur today.  Most of that is related to increases in population and wealth, as the Assessment reports.  We can lessen impacts by hardening our infrastructure (taking the likeliest climate effects into account) today while simultaneously mitigating future climate effects.  One should not happen without the other, but at a minimum, we need to adapt to today’s climate while recognizing tomorrow’s climate will be different.


I want to cite the impacts the Assessment identifies for the Southwest, which includes California, Nevada, Utah, Colorado, New Mexico, and Arizona.  This region is the hottest and driest of the US.  They include: “increased heat, drought, insect outbreaks, and wildfires.  Declining water supplies, reduced agricultural yields, health impacts in cities due to heat, and flooding and erosion in coastal areas are additional concerns.”

Key messages:

  • Reduced snowpack and streamflow
  • Agricultural threats
  • Increased wildfire
  • Sea level rise
  • Heat threats to health

Southwest Responses

I really want to highlight one of the responses.  Without having read through all the responses carefully, I want to point out that I hope other responses are better than this one.  The selected response shows one scenario that could theoretically achieve 80% GHG reductions from 1990 levels by 2050:

 photo SW_energy-generation-by-2045_12447_v10-hi_0_zps2c73bc2c.jpg

I’ll discuss Colorado here; the Assessment included references to exhaustive reports for California, which I’ll cover in the future.

The latest data for Colorado’s net generation shares (2012) demonstrate the immense challenge confronting the scenario shown above.  Broken down by percentage: coal (64.3%), natural gas (20.1%), wind (11.2%), hydroelectric (3.7%), solar (0.3%), biomass and other (0.1% each).  The scenario above (still trying to pin down units) shows that wind can become the dominant source of electricity generation.  In principle, I agree.  But wind would have to switch places with coal as the dominant generation type by 2050 to achieve 80% GHG reductions.  Wind has penetrated the electricity generation market, which I fought for and applaud.  But it still trails natural gas (1/2 the generation) and significantly trails coal (1/5 the generation).  Changing those ratios requires a policy upheaval which I don’t think is likely.  Renewables will eventually supplant fossil fuels as primary generation technologies.  At this time, I don’t think it will happen in Colorado or anywhere else (California has an outside shot) by 2050.


This Assessment is useful for academics and activists, but is probably not useful for the general public.  A brief review of the Response section didn’t convince me that the writers and editors had the public as their primary audience.  I’ve seen Twitter explode today with comments regarding how people were at the forefront of this report, how actionable the information is, etc.  I’m not convinced yet.  Hopefully that will change.

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One thought on “2014 US National Climate Assessment Released

  1. Pingback: April 2014 CO2 Concentrations: 401.33ppm | Weatherdem's Weblog

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