Tag Archives: drought

Chile’s Devastating Fires: Another Climate Change Story

There have been significant wildfires in Chile since November, and they continue. These are the worst fires Chile has seen in known history, and Chile has been keeping track of its history for quite a while.

Are these fires climate change caused? Apparently so. Chile has had a rain deficit for well over a decade, though it as been extra dry for about five years. Drought experts call it a “mega-drought.” Droughts tend to have climate change links, and this one is no exception. A study from just one year ago links anthropogenic climate change to the drought.

Within large uncertainties in the precipitation response to greenhouse gas forcing, the Southeast Pacific drying stands out as a robust signature within climate models. A precipitation decline, of consistent direction but of larger amplitude than obtained in simulations with historical climate forcing, has been observed in central Chile since the late 1970s. To attribute the causes of this trend, we analyze local rain gauge data and contrast them to a large ensemble of both fully coupled and sea surface temperature-forced simulations. We show that in concomitance with large-scale circulation changes, the Pacific Decadal Oscillation explains about half of the precipitation trend observed in central Chile. The remaining fraction is unlikely to be driven exclusively by natural phenomena but rather consistent with the simulated regional effect of anthropogenic climate change. We particularly estimate that a quarter of the rainfall deficit affecting this region since 2010 is of anthropogenic origin. An increased persistence and recurrence of droughts in central Chile emerges then as a realistic scenario under the current socioeconomic pathway.

Heat on top of the drought adds to the likelihood of fires. Decreased snow pack from reduced rainfall and increasing temperatures at altitude also contribute.

Here is the Climate Signals attribution schematic for this event. Click through to climate signals for more.

New climate study is frenemy of climate science driven policy

There is a new study out in Nature that is liable to be misinterpreted, or that may be flawed in a way that lends itself to misuse, in the context of climate science driven policy.

The study is “Northern Hemisphere hydroclimate variability over the past twelve centuries” by Fredrik Charpentier Ljungqvist, Paul J. Krusic, Hanna S. Sundqvist, Eduardo Zorita, Gudrun Brattström & David Frank

I’ll make just a few comments here, but mainly, I want to point you to comments by climate scientist Michael Mann (author of The Hockey Stick and the Climate Wars: Dispatches from the Front Lines and Dire Predictions, 2nd Edition: Understanding Climate Change).

The main question related to policy is this. Do warmer conditions such as we are experiencing now as a result of human greenhouse gas pollution change the hydrology of the planet? The answer, based on various research projects, is yes. Two main things seem to pertain. First, there is more moisture in the air owing to the air being warmer and sea surface temperatures being higher. More moisture holding capacity and more evaporation (movement of water into the air as vapor) result in this effect. At the same time, changes in weather patterns can clump a good amount of this moisture up, so even a modest amount of increase in atmospheric moisture can (and does) result in major precipitation events, causing flooding and other untoward events. This clumping can also serve to deprive some areas of moisture for extended periods of time, and major droughts such as in the Middle East and California are attributed at least in part to this effect.

The study seems to show that this is not likely. The study looks at paleo data over thousands of years, testing and extending a model to apply to present and future climates. The result seems to show that the more extreme changes in hydrology, either wetter or dryer, are not likely. However, Mann makes the point that the kind of data used in this study, such as tree rings, do not reliably show extreme events. In other words, extreme events in the past likely happened without leaving much of a signal.

Mann’s comments are in a facebook post partly reproduced here:

…The study represents a laudable effort to document past changes in extreme rainfall and drought using paleoclimate proxy data, but there are some shortcoming with the study, and especially with the way it is being billed by some of the study’s authors and certain organizations.

A press release from the international paleoclimate organization ?#?PAGES? is accompanied by the rather bold headline “Climate models overestimate twentieth century wet and dry climate extremes”. The lead author Fredrik Ljungqvist is quoted in the press release stating that the discrepancy between the smaller hydroclimatic variations shown by their paleoclimate proxy reconstruction and the greater variations shown by climate models imply that “Climate models strongly overestimate the intensification of wet and dry extremes in the twentieth century”.

Does this study in fact meet the burden of establishing that models are overestimating extremes in rainfall and drought?

Almost certainly *not*.

The discrepancy could arise, of course, from the opposite problem: that the paleoclimate proxy data are *underestimating* hydroclimatic extremes. In my view, that is a far more likely explanation.

Our own extensive work analyzing paleoclimate proxy data has shown has demonstrated they are not well suited for reconstructing past climate *extremes*. Tree rings and many other chemical and biological climate proxy records, by their nature, tend not to record very large short-term fluctuations, and for this reason they are likely to show muted extremes, i.e. less extreme variation than actually exists in the climate record. We published several articles demonstrating this problem over the past several years:

  • Schurer, A., Hegerl, G., Mann, M.E., Tett, S.F.B., Separating forced from chaotic climate variability over the past millennium, J. Climate, 26, 6954-6973, 2013.
  • Mann, M.E., Rutherford, S., Schurer, A., Tett, S.F.B.,Fuentes, J.D., Discrepancies between the modeled and proxy-reconstructed response to volcanic forcing over the past millennium: Implications and possible mechanisms, J. Geophys. Res. 118, 7617-7627, doi:10.1002/jgrd.50609, 2013.
  • Mann, M.E., Fuentes, J.D., Rutherford, S., Underestimation of Volcanic Cooling in Tree-Ring Based Reconstructions of Hemispheric Temperatures, Nature Geoscience, 5, 202-205, 2012.
  • (all available here)

    So, in conclusion, it would be rather dangerous to extrapolate from this one potentially flawed new paleoclimate study any sweeping conclusions about climate models and human-caused climate change. Such over-interpretations of paleoclimate data poorly serve the critical public discourse over the impacts of climate change, and can in fact do harm to the paleoclimate discipline by publicizing bold but unsubstantiated claims that are very likely to be refuted by further work.

    California Levees In Trouble From Drought

    What’s worse than months or years without rain? Rain, after months or years, at least under some circumstances.

    For instance … it gets try, plants become vulnerable to fire. Fires happen denuding the dry landscape. Then it rains, and you get more severe floods together with landslides. You know the story because for years this has been the pattern in California.

    But there is another roughly similar, or at least analogous, problem that is now being discussed. The levees that are mean to keep floodwaters contained in California were already in fairly bad shape. Prior to the drought, a significant number of levees were known to be at risk of failure should they actually get used. Many are thought unable to handle earthquakes as well.

    But with the drought, several factors have probably made the levees weaker. This is an ongoing process and will continue as long as the drought continues.

    From a letter to science, “Drought threatens California’s levees” by Farshid Vahedifard, Amir Aghakouchak, and Joe Robinson,

    Prolonged droughts undermine the stability of levee systems by increasing water seepage through soil, soil cracking, soil strength reduction, soil organic carbon (SOC) decomposition, and land subsidence and erosion . The sand-clay mixtures, which form the body of the levees and consequently the entire structure, can lose a substantial amount of strength under dry conditions. Furthermore, levees in California are built on peaty soils, and the extreme drought leads to greater SOC decomposition in these soils. A large amount of the global carbon stock is found in peaty soils, and ~25% of this estimated stock is predicted to diminish under extremely dry conditions. Oxidation of SOC under a prolonged drought can also accelerate land subsidence. In fact, 75% of the land subsidence across California is accredited to oxidation of SOC. Land subsidence can increase the risk of water rising over the top of the levees.

    This happened in Australia. Remember the big flooding a couple of years back? Some of that was made worse by levees failing, and those levees had been weakened by prolonged drought. So this is not theoretical.

    Global Warming Is Heating Up

    Humans have been releasing greenhouse gas pollution into the atmosphere for a long time now, and this has heated up the surface of the planet. This, in turn, has caused a number of alarming changes in weather. Several current weather events exemplify the effects of climate change.

    Record High Temperatures Being Shattered

    South Asia recently experienced a number of killer heatwaves, and that is still going on in the region. More recently, we’ve seen long standing record highs being broken in the American West. The Capital Climate group recently tweeted this list of records:

    Screen Shot 2015-07-01 at 7.17.01 PM

    Hot Whopper puts this in some context and adds some other sources, here.

    The Weather Channel has this map of current western heat alerts:


    More on the western heat wave here at Weather Underground.

    The extreme heat has even surged north into Canada. Cranbrook, in far southeast British Columbia at an elevation of about 3,000 feet, set a new all-time record high of 98 degrees (36.8 degrees Celsius) Sunday, according to The Weather Network.

    Even Revelstoke, British Columbia – 130 miles north of the U.S. border, about 1,500 feet above sea level and better known for skiing – reached an amazing 103 degrees (39.5 degrees Celsius) Sunday.

    Great Britain is sweltering “on the hottest July day on record,” according to Jessica Elgot at the Guardian.

    As temperatures reached 36.7 °C at Heathrow, commuters were facing difficult journeys on the London Underground. One platform at Kings Cross underground station recorded 33 °C however the temperature on tubes is believed to be even hotter.

    Charlotte Dalen, originally from Norway but now living in London, said: “It was pretty warm and very smelly. People were waving pamphlets to keep cool but it didn’t look like it was helping.”

    The map at the top of the post of current heat anomaly estimates across the globe is from Climate Reanalyser.

    An Unprecedented Tropical Cyclone

    Raquel is a Pacific Tropical Cyclone (hurricane) which is the earliest to form in the region (The “Queensland Zone” as tracked by the Australian meteorologists) in recorded history. From the Bulletin:

    TROPICAL Cyclone Raquel has formed in the south-west Pacific near the Solomon Islands, triggering the earliest cyclone warning on record issued for the Queensland zone.

    “Certainly it’s a unique scenario,” Jess Carey, a spokesman from the bureau’s Queensland office, said. “Since we’ve been tracking cyclones with satellite-based technology, we haven’t seen one in July.”

    The storm became a category 1 cyclone early on Wednesday morning and had a central pressure of 999 hPa about 410 km north of the Solomon Islands’ capital of Honiara as of just before 5am, AEST, the Bureau of Meteorology said. It is forecast to strengthen to a category 2 system on Thursday.

    “The cyclone is moving southwest at about 16 km per hour and should gradually intensify over the next 24 hours as it approaches the Solomon Islands,” the bureau said in a statement. “The system will remain very far offshore and does not pose a threat to the Queensland coast.”

    The official cyclone season runs from November 1-April 30. Any cyclone after May or before October is considered unusual.

    Wildfires Gone Wild

    Over the last several days and continuing, there have been extensive and unprecedented fires in the west as well. Drought in California has increased fire danger, and now things are starting to burn. This year the fires started earlier, with one of the largest fires having burned during a normally low-fire month, February. Also, fires are burning where they are normally rare. According to Will Greenberg at the Washington Post..

    Cal Fire has already responded to 1,000 more incidents this year than they see on average annually. The agency reached that same landmark last year as well — but in September.

    By the end of June, officials had fought nearly 3,200 fires.

    In total, Cal Fire and the U.S. Forest Service have responded to fires stretching over 65,755 acres so far this year.

    And this is just the beginning for California’s 2015 wildfire season.

    Meanwhile, in Washington, where it has been dry and hot, hundreds have been forced to flee from some amazing wildfires. From the Guardian:

    The wildfires hit parts of central and eastern Washington state over the weekend as the state is struggling with a severe drought. Mountain snowpack is at extremely low levels, and about one-fifth of the state’s rivers and streams are at record low levels.

    Eastern Washington has been experiencing temperatures into the 100s, and last week Washington governor Jay Inslee issued an emergency proclamation that allows state resources to quickly be brought in to respond to wildfires.

    In Alaska,

    The number of Alaska’s active wildfires is literally off the charts, according to a map recently released by the state’s Division of Forestry.

    Over 700 fires have burned so far this summer, the most in the state’s history, and that number is only expected to get bigger as the state is experiencing higher temperatures, lower humidity and more lightning storms than usual, said Kale Casey, a public information officer for the Alaska Interagency Coordination Center, which serves as a focal point for state agencies involved in wildland fire management and suppression.

    Here’s a map of current Alaskan fires:
    Screen Shot 2015-07-01 at 7.35.08 PM

    California Drought Still A Drought

    And, of course, from the US Drought Monitor
    Screen Shot 2015-07-01 at 7.36.52 PM

    US Drought Over Time

    I made a movie you might enjoy. There may be something else out there like this, probably better than this one, but it is still cool. I downloaded all the PDF files from the US Drought Monitor archives, using the version of the connected US that has only the year, month, and day on the graphic. Then I slapped them in iMovie and sped the animation up by 800% over the default 1 sec. per pic. I do not have today’s rather horrifying image on it, which I’ve placed above.

    Here’s the movie:

    Climate Change Worsens Drought, Strains Economy….

    Here we have a nice new infographic for you to gaze at, share around on your facebook accounts, and so on. (It is below.) Here in Minnesota, we’ve got a problem getting that last one million acres of corn planted (about 1/8th of the normal amount), not because of drought, but because of excessive rain. However, all that extra rain is not expected to alleviate the effects of our drought long term, so we get to have both. If the price or availability of major food types (“commodities”) goes south (up and down, respectively) here and there, adjustments can be made. But if climate change induced shortages happen in several places at once, what happens then?

    Anyway, here’s the graphic from Climate Nexus:


    I didn't realize the New Scientist was a tool of climate science denialism: The question of drought

    I would almost count it unethical that the New Scientist has a thing that looks like a blog post (an article you can comment on) that has some science in it, but that you have to be a paid subscriber to comment on. WTF New Scientist? What are you trying to pull?

    But that’s OK, I’ve got a blog and can comment here.

    Link between global warming and drought questioned
    14 November 2012 by Fred Pearce

    THE world has been suffering more droughts in recent decades, and climate change will bring many more, according to received wisdom.

    “Received Wisdom” means stuff we were told, passed down to us from authority or tradition, that we accept generally unquestioned and that becomes part of our belief system even if the science or other data does not support it. Pearce either thinks that the global warming-drought link was made up and passed on (by whom? I don’t know) as opposed to being the result of consideration and research by involved and knowledgeable scientists, or he does not know what “Received Wisdom” means. Either way, this should be clarified.

    Now it is being challenged by an analysis that questions a key index on which it is based.

    Predictions of megadroughts affecting Africa and the western side of North America may be wrong. We could even be headed for wetter times, says Justin Sheffield of Princeton University.

    What you are seeing here is a misdirection used by many climate change science denialists, having to do with the time frame of global warming. Droughts affecting Africa are predicted? Sorry, guy, but they’ve happened already and are in progress now. The link between global warming and drought has to do with the regional water cycle, and the idea that if things warm up you get more evaporation in some regions and higher concentration of rainfall, so drought and floods ensue. If you look at the temperature-specific effects of global warming by region, you’ll see that certain areas of Africa and souther hemisphere land masses show more warmth earlier, and they also show more drought earlier. The idea that the effects of global warming are something of the future is a standard denialist lie, and I’m thinking Fred Pearce doesn’t know that. Droughts in Africa, the circum Mediterranean region, and Australia are old news, and the link to global warming is highly likely.

    The problem with the PDSI, says Sheffield, is that it does not directly measure drought. Instead, it looks at the difference between precipitation and evaporation. But since evaporation rates are hard to determine, it uses temperature as a proxy, on the assumption that evaporation rises as it gets hotter.

    Mostly, that is a reasonable assumption, holding ambient moisture in the air constant, because of physics and stuff.

    Sheffield points out that temperature is only one factor influencing evaporation. He inferred evaporation rates using the Penman-Monteith equation, which includes factors such as wind speed and humidity, and found “little change in global drought over the past 60 years” (Nature, DOI: 10.1038/nature11575). His new calculations back up his own previous analysis that the most significant of recent droughts mostly occurred in the 1950s and 60s, before global warming got going.

    If global warming increases evaporation and changes the water cycle to cause drought, then why have we ruled out droughts in the 50s and 60s as irrelevant? There is a general pattern. Climate on a round planet with a sun (like this one) will tend to be driven by equatorial factors, and similarly, the effects of global warming have probably worked their way out from the equator. Ruling out drought in the 50s and 60s, one hundred years after the start of wholesale burning of coal, is rather absurd. Some effects of Global Warming have become very strong in recent decades, especially in the Arctic, but others have been more slow and steady during the entire time of industrial burning of mainly coal. Sea level rise should give a good indicator of whether or not Global Warming is a thing that only counts from 1970, as the article implies. Let’s have a look at that:

    I chose that graph because it is one used by global warming denialists to deny that global warming is real by pointing out that an alleged change that would come with global warming happened before their imagined start of climate change (recently). But no, this is a phenomenon that has been going on for a while.

    So, no, major events that have fundamentally changed the distribution of bioms in the 1950s and 60s near the Equator can not be disassociated from this process.

    It may well be that the PDSI is not the best measurement for drought, but the arguments made here by the New “Scientist” reek of global warming denialist illogic. I look forward to a spirited discussion among actual drought experts over the coming days. If there is something interesting, I’ll report back.

    Meanwhile, New Scientist, you should let people comment on the stuff you put out freely. Paid-to-comment in a world where no one else does that produces the appearance of bias. I would think you would not want to do that.