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Bridging climate science, citizens, and policy


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Climate and Energy Topics – 21 May 2014

The New York Times’ Andy Revkin had this very interesting post last week: “Three Long Views of Life With Rising Seas“.  He asked three folks for their long-term view on how human might deal with the centennial-scale effects of Antarctic glacier melt.  Some of their (partial) responses merit further thought:

Curt Stager, Paul Smith: Imagine the stink we would all raise if another nation tried to take even one inch of our coastline away from us – and yet here is a slow taking of countless square miles from our shores by a carbon-driven ocean-turned-invader.

David Grinspoon: But I think if our society is around for several more centuries we will have to have found different ways to deal collectively with our world-changing technologies. If we’ve made it that far, we’ll find ways to adapt.

Kim Stanley Robinson: It was when the ice core data in Greenland established the three-year onset of the Younger Dryas that the geologists had to invent the term “abrupt climate change” because they had so frequently abused the word “quick” sometimes meaning several thousand years when they said that. Thus the appearance of “Abrupt Climate Change” as a term (and a National Research Council book in 2002).

Andy Revkin finished with: The realities of sea-level rise and Antarctic trends and China’s emissions, etc., make me feel ever more confident that the [bend, stretch, reach, teach] shift I charted for my goals in my TEDx talk (away from numbers and toward qualities) is the right path.

Chinese coal use almost equals that of the rest of the world combined, according to the EIA:

 photo ChineseCoalUsage20140521_zpsac73e973.png

This is but one reason I believe <2C warming is already a historical consideration.  All of this coal production and consumption would have to stop immediately if we have any hope of meeting this political goal.  That will not happen – absent coal generated power, which constitutes the majority generated, the global economy would spin into a depression.

On the good news front, U.S. consumers are expanding home energy efficiency and distributed power generation, according to Deloitte.  These practices started with the Great Recession, but for the first time are continuing after the economy “recovers”.  In 2013, new solar growth occurred among families making between $40,000 and $90,000.  The most engaged demographic could be Generation Y: “1/3 said they “definitely/probably” will buy a smart energy application, which is up from 28 percent in 2011.”

I’ve let my drought series lapse, but have kept watching conditions evolve across the country.  California has obviously been in the news due its drought and wildfires.  All of California is currently in a “severe” drought for the first time since the mid-1970s (see picture below).  So the quick science point: this has happened before (many times; some worse than this) and isn’t primarily caused by anthropogenic forcing.  The quick impacts point: California’s population is double today what it was in the mid-1970s.  Therefore, the same type of drought will have more impact.  Wrapping these points together: drought impacts could be greater in the 2010s than the 1970s due to sociological and not physical factors.  An important caveat: Californians are more adept now at planning for and responding to drought.  They recognize how dry normal conditions can get and have adapted more so than other places in the U.S.  Drought conditions likely won’t improve until this winter during the next rainy season since last winter was a bust for them.

 photo CAdrought20140521_zpsd403ee59.jpg

An incredible story comes from the New York Times about what it takes to engage communities on climate and energy issues.  Nebraska farmers and ranchers are fighting against the Keystone XL pipeline.  Why, you might ask?  Well, they’re certainly not a bunch of hippie greens.  No, they’re responding to their lifestyle and value system.  If KXL is built, it will be built on their land.  That means someone will take away small pieces of a bunch of farmers land, because the locals have already refused $250,000 payments for them.  If KXL is built, it will risk locals’ cattle.  Who do you think will suffer if the pipeline leaks?  The cows, the ranchers, and the Ogallala Aquifer of course.  A critical piece of the paper is this:

Here was one of the best stories she’d ever seen: Conservative American farmers rise up to protect their land. She could use the image of the family farm to reframe the way Nebraskans thought about environmentalism. It wasn’t going to be Save the Sandhill Cranes. It was going to be Save the Neighbors.

To get Nebraskans to respond to environmental issues, you have to engage them on their values, not yours (unless of course you share them).  This is the key that environmentalists have missed for decades and its part of the reason why environmentalism is so politicized.  It’s why conservatives tend not to respond to climate activism framing.

There’s plenty more where this came from.  Stay tuned.


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2014 US National Climate Assessment Released

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.

Southwest

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.

Conclusion

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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California’s Ongoing Drought & Related Climate News

California’s drought is severe and lengthy.  2013 was a record dry year for areas in the state with extensive data records: Los Angeles’s 3.60″ (14.93″ normal) and San Francisco’s 5.59″ (23.65″ normal) among others.  Recent research characterized California as drier than at any time in the past 500 years (an important point that I’ll return to below).  California experienced three consecutive very dry years (2011-2013), and 2014 provided little difference so far.  This dryness and the ensuing drought conditions are part of a longer term decadal-plus drought affecting the southwest US since 2000.

Additional metrics include:

Seventeen rural communities in California are in danger of running out of water within 60 to 120 days, according to a list compiled by state officials. As the drought goes on, more communities are likely to be added to the list.

With only about seven inches of rain in California in 2013 — far below the average of 22 inches — wells are running dry and many reservoirs are about 30 percent full (including Folsom Lake, shown above).

The Sierra snowpack, where California gets about a third of its water, was 88 percent below average as of Jan. 30.

Soon, people will face a lack of fresh water to their homes.  With reservoirs at record low levels, farmers will not be able to plant the crops they want which will reduce our food availability and increase food prices later this year.  This means the impacts will be local and national.  Moving forward, legal fights over very limited water will likely occur.  Folks are about to find out they water they’ve taken for granted is legally obligated to other users.  No one knows what the results will be, but many people have feared this very set of circumstances for a long time.

It would take between 8″ and 16″ of liquid water across most of California to break the drought.  That is unlikely to happen any time soon.  California’s drought is directly related to the snowy winter the eastern half of the nation experienced due to the persistent high-amplitude anomalous jet stream.  High pressure pushed the jet stream to the north over the western US while low pressure allowed the jet stream to dive south over the eastern US.  Usually such a pattern breaks down after a short time.  This winter’s jet stream has been essentially stuck for months now.

In related news, Arctic albedo decreased more than previously thought due to melting Arctic sea ice.  This phenomenon warms the Arctic, including the Arctic Ocean, which affects other parts of the globe, including the US.

And now back to the interesting point I wrote about above: CA is drier than at any point in the past 500 years.  Not forever, 500 years.  That means CA has been this dry in the past (the relatively recent past, in geologic time scales).  Moreover, we should all recall that CO2 concentrations were much lower 500 years ago than they are today.  That means that CA’s dryness is to some extent caused by natural variability.  The scientific question then becomes: “How much?”  Climate attribution studies remain at the forefront of climate research, which is another way of saying we don’t know how much natural variability plays a role in today’s dryness.

A NY Times article captured this recently:

While a trend of increasing drought that may be linked to global warming has been documented in some regions, including parts of the Mediterranean and in the Southwestern United States, there is no scientific consensus yet that it is a worldwide phenomenon. Nor is there definitive evidence that it is causing California’s problems.

The article notes that there are significant similarities between this drought and a similar drought in 1976-77.  What we do know is that temperatures are higher during this drought than they were in 1976-77, which exacerbates the drought’s effects.  What precipitation fell in 2013 evaporated more quickly than before because of warmer temperatures.  So we can say that a similar drought is occurring in a warmer environment, which is something relatively new and noteworthy.

An important point is that this drought is occurring in a world with higher CO2 concentrations than in 1976 or in the 1500s.  But this drought is similar to previous droughts.  Today’s higher CO2 concentrations aren’t the dominant cause of this drought.  Droughts later this century will likely have a more noticeable human fingerprint, but this drought could have (and did) occur in contemporary history.  There is nothing about today’s state of the climate (or 1970’s or 1930’s state of the climate) that precludes this drought.  Quite the opposite is true: this drought belongs to the state of the climate today, not tomorrow.

It is true that the southwest has been in some level of drought condition for 15 years or so.  Those conditions also exist in today’s climate.  They might also exist in the end of the century’s climate, but they will exhibit characteristics that we can’t foresee with any accuracy today.  That said, there are people today in the southwest US that this drought impacts.  That is the reality regardless of the anthropogenic or natural influence on the climate system.  The demand on annual available water now exceeds the supply.  That reality will increasingly shape the southwest in the near future, not the distant future.  Increasingly restrictive water usage policies are more likely than not.


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48.2% of US in Moderate or Worse Drought – 17 Sep 2013 (Thank You, Monsoon!)

According to the Drought Monitor, drought conditions worsened slightly across the entire US compared to three weeks ago. As of September 17, 2013, 48.2% of the contiguous US is experiencing moderate or worse drought (D1-D4), as the early 2010s drought continues month after month.  This value is about 11 percentage points lower than it was in the early spring. The percentage area experiencing extreme to exceptional drought decreased from 14.8% last month to 6.9% last week!  This is more than 10% lower than it was six months ago. The eastern third of the US was wetter than normal during August, which helped keep drought at bay.  The east coast in particular was much wetter than normal and the summer monsoon was much more active this summer compared to 2012, assisted by a persistent upper level blocking pattern.  Instead of Exceptional drought in the West like there was earlier this summer, record rains and flash flooding was the story in September.  While this record-breaking series of events broke the drought in some areas of the West, long-term drought continues to exert its hold over the region.  Compared to earlier this summer, drought increased in area and intensity across the Midwest.

 photo USDrought20130917_zps29a0436a.gif

Figure 1US Drought Monitor map of drought conditions as of September 17th.

If we compare this week’s maps with previous dates (here and here, for example), we can see recent shifts in drought categories.  Compared to mid-August and early September, and despite recent rain events, drought expanded or worsened in the Midwest (Iowa, Missouri, Illinois, Minnesota, and the Dakotas) as well as Louisiana, Arkansas, and Mississippi.  On the other hand, alleviation is evident in small places in the West, as the following map shows.

 photo west_drought_monitor_20130917_zpsd2784c0e.png

Figure 2 – US Drought Monitor map of drought conditions in Western US as of September 17th.

After worsening during late winter into spring 2013, drought conditions steadied in late summer.  The differences between this map and early September’s is the reduction in area and severity of drought, especially in the southern half of the West.  The area experiencing Exceptional drought decreased significantly over the West and the percent area with no drought increased.  Figure 2 also shows that the percent area with no drought is still lower since the start of the calendar year (24% to 18%).

Here are the current conditions for Colorado:

 photo co_drought_monitor_20130917_zps9d17a4ef.png

Figure 3 – US Drought Monitor map of drought conditions in Colorado as of September 17th.

There is evidence of substantial improvement in Colorado since just a few weeks ago and certainly compared to earlier this year, when drought conditions were their worst.  Compared to the start of the calendar year or even three months ago, the percent area of every drought category decreased significantly.  Only 1.5% of the state currently has Exceptional drought.  Only 84% of the state is even experiencing any drought condition today, a far cry from the 100% that lasted for well over one year.  The links in the first paragraph dealing with last week’s rains combine with this graphic to demonstrate that places that receive one year’s worth of precipitation in one week’s time bust their drought!  Many communities would trade those record rains for a little bit of drought, given the extensive damage to infrastructure and the eight people who, as of this morning, perished in the severe weather event.

Let’s compare Figure 3 to similar Colorado maps from earlier in the year.  First, this is what conditions looked like just two weeks ago:

 photo CO_drought_monitor_201309033_zps07464c14.png

Figure 4 – US Drought Monitor map of drought conditions in Colorado as of September 3rd.

The over-active monsoon season helped reduce drought severity from Denver northwest toward the Wyoming border.  I said at the time I hoped that trend continued, but I could never imagine what would happen in the interim.

Here is a look at some of the worst drought conditions Colorado experienced in the past year, from late April 2013:

 photo CO_drought_monitor_20130425_zpsbf9ccb2d.png

Figure 5 – US Drought Monitor map of drought conditions in Colorado as of April 25th.

Conditions were horrible earlier this year.  Reservoir levels declined and crops failed as a result of the higher than normal temperatures and much lower than normal precipitation.  I certainly don’t want to see additional flooding, but I would like to see normal precipitation return to the state and the region.

 photo midwest_drought_monitor_20130917_zpsf91b6be4.png

Figure 6 – US Drought Monitor map of drought conditions in the Midwest as of September 17th.

Drought expanded in the Midwest in the past two weeks: the percent area with no drought decreased significantly from 48% to 43%.  Three months ago, the value was 93%.  This region collected rainfall this month, but the amounts continued to track below average.

 photo south_drought_monitor_20130917_zps76d5a2cf.png

Figure 7 – US Drought Monitor map of drought conditions in the South as of September 17th.

Compared to early summer, drought as a whole expanded across the South in 2013.  Instead of 44% area with no drought three months ago, there is only 16% today.

Policy Context

US drought conditions are more influenced by Pacific and Atlantic sea surface temperature conditions than the global warming observed to date.  Different natural oscillation phases preferentially condition environments for drought.  Droughts in the West tend to occur during the cool phases of the Interdecadal Pacific Oscillation and the El Niño-Southern Oscillation, for instance.  Beyond that, drought controls remain a significant unknown.  Population growth in the West in the 21st century means scientists and policymakers need to better understand what conditions are likeliest to generate multidecadal droughts, as have occurred in the past.  Without comprehensive planning, dwindling fresh water supplies will threaten millions of people.  That very circumstance is already occurring in western Texas where town wells are going dry.  An important factor in those cases is energy companies’ use of well water for natural gas drilling.  This presents a dilemma more of us will face in the future: do we want cheap energy or cheap water?  In the 21st century, we will not have both options available at the same time as happened in the 20th century.  This presents a radical departure from the past.

As drought affects regions differentially, our policy responses vary.  A growing number of water utilities recognize the need for a proactive mindset with respect to drought impacts.  The last thing they want is their reliability to suffer.  Americans are privileged in that clean, fresh water flows every time they turn on their tap.  Crops continue to show up at their local stores despite terrible conditions in many areas of their own nation (albeit at a higher price, as found this year).  Power utilities continue to provide hydroelectric-generated energy.

That last point will change in a warming and drying future.  Regulations that limit the temperature of water discharged by power plants exist.  Generally warmer climate conditions include warmer river and lake water today than what existed 30 years ago.  Warmer water going into a plant either means warmer water out or a longer time spent in the plant, which reduces the amount of energy the plant can produce.  Alternatively, we can continue to generate the same amount of power if we are willing to sacrifice ecosystems which depend on a very narrow range of water temperatures.  As with other facets of climate change, technological innovation can help increase plant efficiency.  I think innovation remains our best hope to minimize the number and magnitude of climate change impacts on human and ecological systems.


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50.1% of the Contiguous United States in Moderate or Worse Drought – 3 Sep 2013

According to the Drought Monitor, drought conditions worsened slightly across the entire US compared to three weeks ago. As of September 3, 2013, 50.1% of the contiguous US is experiencing moderate or worse drought (D1-D4), as the early 2010s drought continues month after month.  This value is about 9 percentage points lower than it was in the early spring. The percentage area experiencing extreme to exceptional drought decreased from 14.8% three weeks ago to 9.9% last week; this is approximately 10% lower than it was six months ago. The eastern third of the US was wetter than normal during August, which helped keep drought at bay.  The east coast in particular was much wetter than normal and the summer monsoon was much more active this summer compared to 2012.  Instead of Exceptional drought in Georgia and Extreme drought in Florida two years ago, there is flash flooding and rare dam water releases in the southeast.  Four eastern states experienced their top-four wettest Julys on record.  The West presents a different story.  Long-term drought continues to exert its hold over the region, as it remained warmer than normal but six southwestern states received top-20 July precipitation this year.  Meanwhile, Oregon recorded its driest July on record.  Compared to three weeks ago, drought area increased in the Midwest.

 photo USDrought20130903_zpsf4845451.gif

Figure 1US Drought Monitor map of drought conditions as of September 3rd.

If we compare this week’s maps with previous dates (here and here, for example), we can see recent shifts in drought categories.  Compared to early July and mid-August, and despite recent rain events, drought expanded or worsened in the Midwest (Iowa, Missouri, Illinois, Minnesota, and the Dakotas) as well as Louisiana, Arkansas, and Mississippi.

 photo west_drought_monitor_20130903_zps6a3a6205.png

Figure 2 – US Drought Monitor map of drought conditions in Western US as of September 3rd.

After worsening during late winter into spring 2013, drought conditions steadied during the past month.  The differences between this map and mid-August’s is the spatial shift of conditions; the total percent area values are about the same.  The area experiencing Exceptional drought decreased slightly over the West and the percent area with no drought increased slightly, but remains at low levels.  Figure 2 also shows that the percent area with no drought decreased since the start of the year (24% to 14%).

Here are the current conditions for Colorado:

 photo CO_drought_monitor_201309033_zps07464c14.png

Figure 3 – US Drought Monitor map of drought conditions in Colorado as of September 3rd.

There is clear evidence of relief evident over the past three months here.  Severe drought area dropped from 72% to 60% (this was 100% about last year!).  Extreme drought area dropped from 27% to 22% (also down from 50%+ six months ago).  Exceptional drought decreased significantly from three and six months ago.  Instead of 16% of Colorado (and as much as 17% earlier this year), Exceptional drought now covers only 3% of the state.  The good news for southeastern Colorado was the recent delivery of substantial precipitation.  I didn’t think it would be enough to completely alleviate the worst conditions, but they received enough precipitation that drought conditions improved from Exceptional to Extreme.  Their drought is not over yet, but they are finally trending in a good direction.  And for the first time in over one year, some small percentage (2%; up from 1% three weeks ago) of Colorado does not currently have any drought.  This is great news – hopefully this area expands throughout the rest of the year.

 photo midwest_drought_monitor_20130903_zpseafbaad1.png

Figure 4 – US Drought Monitor map of drought conditions in the Midwest as of September 3rd.

Drought expanded and worsened slightly in the Midwest in the past few months: the percent area with no drought decreased significantly from 91% to 52%.  The percent area with Moderate drought increased significantly from 3% to 29% this week.  Severe drought now impacts most of Iowa and small portions of Missouri, Wisconsin and Minnesota.

US drought conditions are more influenced by Pacific and Atlantic sea surface temperature conditions than the global warming observed to date.  Different natural oscillation phases preferentially condition environments for drought.  Droughts in the West tend to occur during the cool phases of the Interdecadal Pacific Oscillation and the El Niño-Southern Oscillation, for instance.  Beyond that, drought controls remain a significant unknown.  Population growth in the West in the 21st century means scientists and policymakers need to better understand what conditions are likeliest to generate multidecadal droughts, as have occurred in the past.  Without comprehensive planning, dwindling fresh water supplies will threaten millions of people.  That very circumstance is already occurring in western Texas where town wells are going dry.  An important factor in those cases is energy companies’ use of well water for natural gas drilling.  This presents a dilemma more of us will face in the future: do we want cheap energy or cheap water?  In the 21st century, we will not have both options available at the same time as happened in the 20th century.  This presents a radical departure from the past.

As drought affects regions differentially, our policy responses vary.  A growing number of water utilities recognize the need for a proactive mindset with respect to drought impacts.  The last thing they want is their reliability to suffer.  Americans are privileged in that clean, fresh water flows every time they turn on their tap.  Crops continue to show up at their local stores despite terrible conditions in many areas of their own nation (albeit at a higher price, as found this year).  Power utilities continue to provide hydroelectric-generated energy.

That last point will change in a warming and drying future.  Regulations that limit the temperature of water discharged by power plants exist.  Generally warmer climate conditions include warmer river and lake water today than what existed 30 years ago.  Warmer water going into a plant either means warmer water out or a longer time spent in the plant, which reduces the amount of energy the plant can produce.  Alternatively, we can continue to generate the same amount of power if we are willing to sacrifice ecosystems which depend on a very narrow range of water temperatures.  As with other facets of climate change, technological innovation can help increase plant efficiency.  I think innovation remains our best hope to minimize the number and magnitude of climate change impacts on human and ecological systems.


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4th Daily April Record Low in Denver & Record Snow in Boulder

I spent a lot of time on record temperatures in Colorado in 2012 – they were all record highs.  Due to annual weather variability, there are a couple of different records in April 2013: record lows.  There have been four record lows set or tied in Denver, CO this April:

9F on April 9th

6F on April 10th

22F on April 16th (tie)

21F on April 22nd

Needless to say, with record low temperatures due to vigorous synoptic cyclones that brought Arctic air masses down into the middle of the country, April’s average temperature is among the lowest on record.  I will have more to say about that next week after the month ends.  Denver may not record a bottom-10 moth because much more seasonable weather is on tap for the next week.  In contrast, two record highs were set in April 2012: 84F on the 1st and 88F on the 24th.

In other news, Boulder, CO set a monthly record for snowfall: 47.4″ through the 23rd!  The old record of 44″ was set in 1957.  The official snowfall measurement site for Denver (Denver Int’l Airport) recorded “only” 20.4″ of snow for the month-to-date.  With 60F+ temperatures forecasted from today through next Tuesday, DIA won’t challenge the top-10 snowiest Aprils (#10 recorded 21.0″ of snow).

Remember that one month’s, season’s or year’s temperatures, precipitation, or even drought are not indicative by themselves of climate change.  They are too heavily influenced by individual weather systems.  When I discuss climate change, I write about long-term trends (decadal to multi-decadal).  Natural variability influences individual weather events that overlie the long-term climate signal.  I’ve written before that climate change means we are more likely to see record high temperatures than record low temperatures.  The weather will continue to set both, but will set the former at a higher rate moving forward than the latter.  Of course, I for one am very glad there was more precipitation than normal for April.  Last year’s drought and record hot summer was not enjoyable to live through.  Denver-Boulder and the surrounding region will unfortunately need months in a row of above average precipitation to break the long-term drought.  This spring’s precipitation pattern slightly reduced the intensity and areal coverage of drought.  I will update my last drought post in the next couple of days.


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No Significant Climate Change Signal In 2012 US Drought

A team of atmospheric scientists, led by the National Oceanic and Atmospheric Association, issued a report this week that presented initial results of an examination into the extreme 2012 US drought.  Its core finding was the drought likely resulted mostly from natural variability.  Any climate change signal is relatively small but likely made conditions across the Midwest US a little dryer and a little warmer than they otherwise would have been absent climate change.

The 2012 drought did not grow out of the 2010-2011 Southern drought that impacted Texas and Oklahoma, as many, including myself, theorized as the drought developed.  Instead, a stubborn ridge of high pressure took hold over the Plains, which cut off the vital Gulf of Mexico water supply upon which the region depends for agriculture.

This sentence, in the Executive Summary, is key: “The interpretation is of an event resulting largely from internal atmospheric variability having limited long lead predictability.”  Many people think severe weather events should be easy to forecast, but the opposite is true.  The rarer the event, the more difficult it is to accurately forecast with any kind of time difference.  Additionally, the connection to low-frequency climate oscillations (i.e., La Niña: “the 2012 drought occurred in concert with an appreciably warmer ocean in most basins than was the case for any prior historical drought”) were minimal in the 2012 drought, contrary to what I have theorized.  That’s the beauty of science, of course.  You can be incorrect about something and demonstrate as such when data are analyzed.

Recently, some folks have characterized this event as a “flash drought”, owing to the sudden onset of such an event, as the first graphic below shows.  The term obviously borrows from the better known “flash flood” concept.  Unlike a flood however, droughts have longer-term impacts on human and ecosystems.  Costs are still only estimated at this time (because the drought is ongoing) at $12 billion.  While significant, the 1980 drought event that caused 56 billion (2012$) and the 1988 drought that caused 78 billion (2012$) of damages eclipsed the 2012 event (so far).  The $12 billion figure is likely to grow as the drought impacts water supply reductions and livestock.  The 2012 crop yield deficit was the greatest since 1866.

 photo 2012Drought-NOAAReport_zpsde8de4b2.png

Figure 1 – U.S. Drought Monitor maps showing the evolution of the 2012 “flash drought” across the US Great Plains.  Little evidence existed in November 2011 or even May 2012 that the drought would achieve the extent and intensity that it did.

The drought was the worst on record for WY, CO, NE, KS, MO, and IA, as the following graphic shows.  The region experienced a 53% rainfall deficit (39.3mm vs. 73.5mm) in 2012.  1934 held the previous record of -28.4mm deficit.  The 2012 deficit corresponds to a 2.7 standardized deficit, which approaches a 1-in-100 event.  This relates well to the precipitation time series in the graph below.

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Figure 2 – Precipitation and temperature departures from normal for the six states impacted by the 2012 drought.  Note the extreme minimum in precipitation on the right side of the top graph.  2012 temperatures as a whole were not as extreme as those recorded twice during the 1930s, but July 2012 still ranks as the warmest month on record for the six states as well as the entire US.

The analysis also suggests that we should not expect similar 2013 precipitation anomalies on the basis of 2012 anomalies alone (based on the report’s Figures 10 and 11).  Put another way, just because 2012 was drier than normal, 2013 shouldn’t automatically be drier also.  Dry epochs occurred in this region before: in the 1930s and 1950s.  Subsequent dry years occurred then due to longer-term changes in natural variability as well as land use practices.  The currently is no indication that the 2010s will similarly be a dry epoch.  As with the 2012 drought, such a prediction remains beyond current skill.

The diagnosed linkage to low-frequency forcing is interesting.  Warm tropical sea-surface temperatures (SSTs) in the Indo-West Pacific Oceans and cold east Pacific conditions tend to dry the mid-latitudes in the winter/spring season and not the summer season.  As the first graphic demonstrates, the 2012 drought flashed in the summer and not the winter.  So despite primed conditions for drying in winter 2011-12, the Great Plains drought occurred for different reasons.

Of further interest to the future is the following graphs.  The researchers generated a 20-member NCAR CAM-4 ensemble with monthly varying SSTs, sea ice, and specified external radiative forcings consisting of greenhouse gases (e.g. CO2, CH4, NO2, O3, CFCs), aerosols, solar, and volcanic aerosols via observations through 2005 and then an emission scenario thereafter (RCP6.0, a moderate emissions scenario pathway developed for the upcoming IPCC’s AR5).

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Figure 3 – Model results of the 1996-2012 precipitation minus the 1979-1995 precipitation.

The NCAR CAM4 model might be representing the actual climate well for this time period.  Left unsaid in the report is any analysis of the model’s future projections.  Other model studies suggest that the central US could experience 2012-type temperature and precipitation conditions more regularly by the end of the 21st century.

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Figure 4 – Model probability density functions of precipitation deficits for the six study states.

This figure suggests that the latter half of the time period (1996-2012) modeled had a higher probability of being drier than did the former half (1979-1995).  The report did not present a potential cause for this shift in probability.  If this probability does not revert back to the 1979-1995 distribution, dry conditions could become a more regular feature of future years.

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Figure 5 – Model probability density functions of precipitation surpluses for the six study states.

This figure is not the logical companion to the previous figure.  The probability of being wetter and drier could increase if the overall probability density function existed in a certain way.    This is not the case however.  Instead, the probability of the six states experiencing wetter conditions in the second half of the period studied decreased with respect to the first half.

This report is useful in diagnosing what happened prior to and during the 2012 US drought and in trying to ascertain how predictable such an event might have been.  There is considerable interest in accurately predicting this type of event well in advance so as to prepare those who might be affected.  This capability remains beyond us for now since this event was primarily driven by natural variability enhanced slightly by underlying change.  With climate model projection studies indicating a much warmer and somewhat drier future for this region, stakeholders will likely have to adapt farming and ranching practices.  Similarly, municipalities will have to prepare for extremely dry years in their infrastructure planning and practices.  Of course, future change could be reduced as a result of our efforts to mitigate anthropogenic forcing.  The scale of that endeavor is much larger than most people are aware and thus not likely to take place any time soon.  Climate and energy policies need significant revamping at all levels.

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