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Climate Hustle

Fire and water – how global warming is making weather more extreme and costing us money

Posted on 2 September 2014 by dana1981

Connecting the dots between human-caused global warming and specific extreme weather events has been a challenge for climate scientists, but recent research has made significant advances in this area. Links have been found between some very damaging extreme weather events and climate change.

For example, research has shown that a “dipole” has formed in the atmosphere over North America, with a high pressure ridge off the west coast, and a low pressure trough over the central and eastern portion of the continent.

Departure of the November 2013 – January 2014 250 hPa geopotential height from the normal climatology. Departure of the November 2013 – January 2014 250 hPa geopotential height from the normal climatology. Source: Wang et al. (2014), Geophysical Research Letters Photograph: Wang et al. (2014), Geophysical Research Letters

These sorts of pressure ridges in the atmosphere are linked to “waves” in the jet stream. Research has shown that when these jet stream waves form, they’re accompanied by more intense extreme weather. The high pressure zone off the west coast or North America has been termed the “Ridiculously Resilient Ridge” due to its persistence over the past two years. It’s been the main cause of California’s intense drought by pushing rain storms around the state.

California drought as of 26 August 2014.  58% of the state is in 'exceptional drought' conditions. California drought as of 26 August 2014. 58% of the state is in ‘exceptional drought’ conditions. Source: United States Drought Monitor

A paper led by S.-Y. Wang of Utah State University found the high pressure ridge is linked to a precursor of the El Niño Southern Oscillation (ENSO), but also that human-caused global warming has amplified the strength of these ridges. The authors concluded,

It is important to note that the dipole is projected to intensify, which implies that the periodic and inevitable droughts California will experience will exhibit more severity.

Similarly, a recent paper led by Kevin Trenberth and published in Nature Climate Change concluded,

Increased heating from global warming may not cause droughts but it is expected that when droughts occur they are likely to set in quicker and be more intense.

Another study recently published in the Journal of Climate examined data from past climate changes, and found that climate models are underestimating the likelihood of intense droughts in the southwestern USA due to global warming.

In the US Southwest, for instance, state-of-the-art climate model projections suggest the risk of a decade-scale megadrought in the coming century is less than 50%; our analysis suggests that the risk is at least 80%, and may be higher than 90% in certain areas. The likelihood of longer lived events (> 35 years) is between 20% and 50%, and the risk of an unprecedented 50 year megadrought is non-negligible under the most severe warming scenario (5-10%).

There are several ways in which global warming intensifies drought. Hotter temperatures increase evaporation from soil and reservoirs. They cause more precipitation to fall as rain and less as snow, which for a region like California that relies on the snowpack in the Sierra Nevada mountains as its natural water storage system, is problematic. Hotter temperatures also cause the snowpack to melt earlier in the year. The problem can be alleviated by building more water storage infrastructure, but that costs money.

On top of all that, there’s the apparent strengthening of high pressure ridges off the coast, pushing rain storms around California. Research suggests that there may be a connection between these ridges and the decline in Arctic sea ice, although this connection is debated among climate experts.

California is the biggest agricultural producer in the USA, and exported $18 billion of agricultural products to the world market in 2012. The state leads the USA in 79 different crop and livestock commodities ranging from artichokes to olives to walnuts. When California agriculture takes a hit due to drought amplified by global warming, it has costs across the country and around the world in the form of higher food prices. A report out of UC Davis also estimated the drought’s cost to the state in 2014 at $2.2 billion.

Much of those costs are related to increased pumping of groundwater. So much groundwater has been pumped over the past 18 months that a recent study found that California has a 63 trillion gallon groundwater deficit. Due to this depletion of groundwater, which is heavy and depresses the planet’s crust, the Sierra Nevada mountains are now up to 15 mm higher than before the drought. The reduced stress on the San Andreas fault has also made earthquakes more likely in California.

Droughts and global warming are also connected to wildfires. Hotter, drier temperatures create conditions ripe for large fires, which have become more common in the western USA over the past four decades.

Annual number of wildfires greater than 1,000 acres on U.S. Forest Service Land Annual number of wildfires greater than 1,000 acres on U.S. Forest Service Land. Source: Climate Central Photograph: Climate Central

A 2011 study published in the journal Climatic Change estimated that in a business-as-usual scenario with continued reliance on fossil fuels, by 2085 the annual area burned by wildfires in California will increase by 40–70% as compared to 1975. If we take serious action to reduce human-caused global warming, the annual area burned can be limited to a 15–30% increase in 2085.

Most of this increase is projected to happen in northern California, where air pollution from those fires tends to collect in the Central Valley, causing adverse health impacts. The property damage caused by the fires, firefighting efforts, and health effects all have significant costs.

Climate scientists have been working on teasing out the global warming contributions to various extreme weather events. They’ve determined that global warming made several specific weather events more likely and/or more extreme; particularly heat waves and flooding.

Peter Stott of the UK Met Office is leading a new project called European Climate and Weather Events: Interpretation and Attribution (EUCLEIA). The idea is to run climate simulations with and without a human-caused global warming component, to see how much more likely climate change has made a particular type of extreme weather event.

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Comments

Comments 1 to 12:

  1. Low pressure features are referred to as troughs rather than ridges.  Otherwise, very interesting article - Thanks! - B

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  2. B, I did not see the equivocation, but not being a scientists, I have little patience meaningless for nitpicking. Although, I know arguing an important fine point is important and valuable.

    The point I take from this is that cost, or money, always goes to energy, and energy use always goes to the lowest cost component, which is usually the most carbon intensive fuel. Further, since the non-monetary costs; fires and increased evapotranspiration also add to the problem, we are in a nasty feedback loop already {:[

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  3. PluviAL,

    The terms "ridge" and "trough" are descriptive.  In an area of high pressure a given pressure is found at a higher elevation than in the surrounding region, hence "ridge"; in a low-pressure area a given pressure is found at a lower elevation than in the surrounding region, so the feature is called a trough.  Ridges and troughs determine wind direction near and around them, and thus the movement of weather systems; the pattern around a ridge is the opposite of the pattern around a trough, and the associated weather is completely different.  As an example:  If the ridge off the west coast of North America had not been there for the past couple of years, or if a trough had been there instead, California would not be in the present devastating drought.

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  4. Very weak and vague statements. Not really convincing.

    Wang of Utah State University found the high pressure ridge is linked to a precursor of the El Niño Southern Oscillation (ENSO)

    El Nino is a natural phenomenon. What's the role o global warming?

    but also that human-caused global warming has amplified the strength of these ridges

    Only "human-caused" warming? Do those ridges know who or what caused warming, if any. How do those ridges sense warming if there hasn't been any over the past almost 2 decades?

    the journal Climatic Change estimated that in a business-as-usual scenario with continued reliance on fossil fuels, by 2085 the annual area burned by wildfires in California will increase by 40–70%

    How do they know what California will look like in 70 years from now? With the ongoing draught, there might nothing be left that could burn. Or one of those earthquakes might have extinguished California alltogether.

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  5. topal - your argument is basically a variant of "its natural". Ie unforced variation. The science says all recent warming is forced (if we didnt have CO2 induced warming we would be cooling). See here for more discussion.

    You can see more discussion of the probability distributions used by IPCC here for attribution.

    In short, what you are seeing is postulated to be due to a warmer ocean. Ocean Heat Content has been steadily increasing. If you think that is "natural", then tell me where the energy stored there is coming from?

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  6. topal @4, it was very nice of you to flag what followed as being "very weak and vague" and "not really convincing".  Given the low opinion you appear to have of the ideas you expressed, one wonders why you bothered.

    Turning to those "not really convincing" arguments, we first have the tried and true tactic from all sorts of deniers of breaking up sentences to remove context.  Thus the first sentence you quote clearly expresses an opinion about the impact of global warming:

    "A paper led by S.-Y. Wang of Utah State University found the high pressure ridge is linked to a precursor of the El Niño Southern Oscillation (ENSO), but also that human-caused global warming has amplified the strength of these ridges."

    You, however, break it at the comma removing the context and then facetiously enquire, "What's the role o global warming?" as if that had not been expressed in the immediately following clause.

    Here's the rule:  Breaking a quote up into individual clauses of sentences to comment inline is always quoting out of context; and when the comment it to ask why something explained in the immediately following clause in not explained in the preceeding clause, the out of context quotation is always dishonest.

    In response to the second clause you ask the inane question, "Only "human-caused" warming?"  Based in the IPCC AR5, anthropogenic warming accounts for 108% of warming from 1950-2010, with the extra 8% countering a probable cooling trend had natural factors alone been acting.  That is well established.  Scientists do not need to repeat the evidence for it every time they mention anthropogenic warming any more than astronomers need to repeat the evidence for heliocentrism everytime they mention a year.

    Nor, as regards your second sally, has the warming from 1950 to 1998 suddenly vanished over the last 15 years, even if we accepted the false proposition that there has been no warming since 1998.

    Finally, as regards to projections you venture that we cannot make such projections because there is a very low probability of much worse catastrophes.  Really?  Are you that short of a decent argument that you have to run that absurdity.  In case you don't get it, if the argument was valid, all planning ever would be pointless for there is always a very low risk ultimate catastrophe that would render it pointless.

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  7. @scaddenp: "Ocean Heat Content has been steadily increasing. If you think that is "natural", then tell me where the energy stored there is coming from?"

    The only source of energy I know of is the sun, do you know of any other source?

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    Moderator Response:

    [Rob P] - Radiative output from the sun has declined in the last 3-4 decades:

    Whereas ocean heat content (OHC) up to June 2014 has undergone substantial warming:

     

     

    It's safe to conclude that the sun is not responsible for ongoing ocean warming. Greenhouse gases on the other hand......

  8. Perhaps an analogy will help Topal.  Imagine there is a person on a single income, who spends some of their money and saves the rest in a zero interest account.  Over a period of years we find out that their savings have increased dramatically.  The question arises, is that because they are earning more?  Or spending less?  Finally, we get access to their wage records which show conclusively that they have actually been earning less.  Clearly the increased savings have come from reduced expenditures.

    Now somebody might want to challenge this on the basis that they only have one source of money (their wage) so that any savings must come from that wage.  In a way that is true.  Never-the-less, it should be clear that it is not the change in wage that has resulted in the increased savings, but the reduction in expenditure.  The person pointing out that any money they save was originally recieved as part of their wage is pointing to an irrelevant fact.

    Increasing CO2 in the atmosphere in fact reduces the energy from the Earth to space, at least initially.  It is analogous to saving more.  Ocean Heat Content is stored energy, so it is analogous to saving, and energy from the Sun is analogous to the single income.

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  9. Topal, if I put a coat on then my skin temperature increases and I feel warmer.   Does this show that my body started producing extra heat when I put the coat on, or is there another explanation?

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  10. I want to commend Tom Curtis for his time relentlessly pointing the irrationality of all denial talking points that appear in SkS comments. Even in case of topal@4, a comment so irrational and absurd that I feel like it barely hangs above the comment policy bar, Tom does not mind typing comprehensive response & debunking the absurdity, as moderation sword could easily cut it. Thank you Tom!

    Maybe topal@4 (and Tom's response) could stay unmoderated as an example of irrational logic or denialist talking points.

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  11. Topal

    ''The only source of energy I know of is the sun, do you know of any other source?'

    Nope. Certainly not large enough. But the sun is a source of energy that flows through the earth and back out to space. If nothing changes the ease with which that flow can occur then the total heat here on earth doesn't change. However if something does change the ease of that flow, like, I dunno, something that restricts the flow back out to space then heat could certainly start to accumulate here.

    Someting like, I dunno, maybe something that increases the effectiveness of the GH Effect!

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  12. Yes thanks Tom for saving me the effot of responding.  It's kind of appalling to delete the part of the sentence that links the event to AGW and then ask where the link is to AGW.

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