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Climate change and consequences on the ground

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The link between extreme weather events, climate change, and national security is discussed in Extreme Realities, a new episode in PBS’ series Journey To Planet Earth hosted by Matt Damon.

The video features a number of extreme weather phenomena: hurricanes, tornadoes, floods, wild fires, and flooding. The discussion is about climate change and the consequences on the ground – or, how climate change may affect you.

It is important to ask what is the story behind the assertions made in the video. What scientific support is there for the link between such extremes and climate change?

Linking global warming to some of these extreme weather and climate phenomena has been tricky in the past. In some cases the record of past events may not be sufficiently complete to identify whether there is a dependency to the global state, mainly because many extremes are both rare and take place at irregular intervals. However, there has been substantial progress over the recent years.

Global climate models may provide a tool for studying such links, but they are designed to provide a picture of general large-scale features such as the greenhouse effect and how the air moves around, rather than local extreme phenomena. For some types of extremes such as heat waves, they can nevertheless provide valuable insight (Hansen et al., 2012).

Heat waves and droughts often extend over space and time, and the global climate models may provide a good representation of droughts and heat waves if they manage to predict the frequency and duration of high-pressure systems and the soil moisture associated with these events.

The way the air flows is in some circumstances difficult to predict, for instance where the storms move (storm tracks) and changes in the large-scale atmospheric circulation. The reason for this is described in earlier posts on chaos and climate, and was first discussed by Lorenz.

The climate models manage to reproduce the Hadley cell, El Nino Southern Oscillation, the Jet streams, the Trades, and the westerlies, but not tornadoes, derechoes, and thunderstorms. They do not provide the details needed to describe the local climate and many extreme phenomena affecting society and ecosystems.

Our knowledge about extremes and climate is based on more evidence than just climate model results. One elegant example is the recent paper in PNAS by Petoukhov et al., (2013) based on mathematics, physics, and measured air flow.

From physics, we know that different conditions such as soil moisture and cloud micro-physics both affect weather extremes, although different types and on different scales. Convective storms and tornadoes, as opposed to heat waves, have in the past gone undetected and tend to pass below the radar of the global climate models.

New studies, such as Petoukhov et al., (2013), are emerging in the scientific literature that provide additional support for a link between climate change and a wider range of extreme phenomena. These are based on our physical understanding, observational data, new ways of analysing data, and attribution studies (Coumou and Rahmstorf, 2012).

We are also learning more about local convective storms, and a recent example is provided by the Swedish Rossby Centre, reporting that showery convective rainfall type intensifies faster than the more spatially extensive stratiform type in response to warmer temperatures (Berg et al., 2013).

The analysis of the past observations has not always given a clear picture. So far, no clear connection has been found between the global warming and mid-latitude storms (or wind speed), and efforts comparing different ways to analyse past storm observations have only recently been published (Neu et al. (2012). If we understand why some analytical methods give different results for past storms, then we will be in a better position to detect potential dependencies to the state of the global climate.

Extreme events are a natural part of the climate system, and a climate change means that their frequencies and intensities may change. Detecting the changes in probabilities in rare events is statistically challenging. However, counting the recurrence of record-breaking extremes can provide an indication of whether the extreme values are changing (Benestad, 2008).

The consequences of a climate change involves some known aspects as well as some which we cannot predict. Extreme phenomena take place in certain environmental conditions, favourable for forming e.g. tornadoes, storms, or droughts. We also know that our models have their limitations, and that the range of possible outcomes can be fairly wide.

The incomplete knowledge is no different to any other field, as the future always seems to involve some surprises. Societies have traditionally tackled the absence of complete certainties by adopting various forms for risk analyses, e.g. fire brigades, police, defence, hospitals, and so on.

Better safe than sorry. Here, there are some known connections of concern. The bottom line is that we need pragmatic ways of dealing with issues that may have devastating effects for people or societies – and this is the red thread in ‘Extreme Realities‘.

References

  1. J. Hansen, M. Sato, and R. Ruedy, "Perception of climate change", Proceedings of the National Academy of Sciences, vol. 109, 2012. http://dx.doi.org/10.1073/pnas.1205276109
  2. D. Coumou, and S. Rahmstorf, "A decade of weather extremes", Nature Climate Change, vol. 2, pp. 491-496, 2012. http://dx.doi.org/10.1038/nclimate1452
  3. P. Berg, C. Moseley, and J.O. Haerter, "Strong increase in convective precipitation in response to higher temperatures", Nature Geoscience, vol. 6, pp. 181-185, 2013. http://dx.doi.org/10.1038/ngeo1731
  4. U. Neu, M.G. Akperov, N. Bellenbaum, R. Benestad, R. Blender, R. Caballero, A. Cocozza, H.F. Dacre, Y. Feng, K. Fraedrich, J. Grieger, S. Gulev, J. Hanley, T. Hewson, M. Inatsu, K. Keay, S.F. Kew, I. Kindem, G.C. Leckebusch, M.L.R. Liberato, P. Lionello, I.I. Mokhov, J.G. Pinto, C.C. Raible, M. Reale, I. Rudeva, M. Schuster, I. Simmonds, M. Sinclair, M. Sprenger, N.D. Tilinina, I.F. Trigo, S. Ulbrich, U. Ulbrich, X.L. Wang, and H. Wernli, "IMILAST: A Community Effort to Intercompare Extratropical Cyclone Detection and Tracking Algorithms", Bulletin of the American Meteorological Society, vol. 94, pp. 529-547, 2013. http://dx.doi.org/10.1175/BAMS-D-11-00154.1
  5. R.E. Benestad, "A Simple Test for Changes in Statistical Distributions", Eos, Transactions American Geophysical Union, vol. 89, pp. 389-390, 2008. http://dx.doi.org/10.1029/2008EO410002

Reader Interactions

118 Responses to "Climate change and consequences on the ground"

  1. Wait — is there evidence that food chains haven’t accumulated any more mercury than they did before coal-burning started?

    Where can I read about this, and what else have they lied to me about?

  2. Also for Chuck Hughes, this climate blogger writes well about how to learn:
    http://angusferraro.wordpress.com/2013/03/29/new-chapters-and-foreign-lands/

    “… In order to interpret my model results I had to learn to thinking differently. Intuitions learned from midlatitude dynamics don’t apply this close to the Equator.

    “Learning new theory can be pretty intimidating. It’s difficult to know which paper to read first. Sometimes I find myself feeling paralysed. I have a pile of things to read but keep having to refer to different sources to understand terminology, or to get to the bottom of some ‘obvious’ physical understanding not fully explained in one piece of research….”

  3. 100 Russell, you HAVE to start giving some sort of evidence. NOTHING posted here shows natural sources are more than a minor component totalling the least harmful 1/3 of Hg emissions. To REFUSE to provide ANY evidence yet bleat that “it’s all natural”, well, it gets frustrating for the rest of us, and we tend to slot “Russell” into the “Fool” bin. (sorry, tis just human nature). Much better would be to actually provide some data or logic, eh? Show us why our initial response was wrong. I’m rooting for ya, kid.

  4. and Russell, by ANY evidence, I mean just that. So far you’ve shown ZERO. So, to buttress your case, ANY thoughts by ANYBODY would suffice. So, troll the web, find ANYBODY who would benefit financially or mentally, and share.

    My guess is you’ll waste a week finding bubkis.

  6. Thanks Hank. Very accessible visual, and fascinating. Hope that stops the yelling and shows that life is complex. We already knew that, but somehow the anti-science contingent always wants to fasten on absolutes (and no, I’m not talking to you, if you think this was addressed to you, most likely).

  7. 103, 104

    The evidence Jim Larsen demanded on 29 March is contained in the very link he provided , but evidently has not troubled to read in full, which gives the range of estimates for both natural and anthropogenic Hg fluxes. If he finds that data hard to deconvolute, he may be in for a shock when he encounters the primary geochemical literature.

    He appears to be comparing the lower outliers instead of the average figures, let alone the higher ones- He will find the ice core record useful in comparing the continuous threat posed by volcanic and hot spring emissions with such intensive but sporadic local fluxes as those associated with the California gold rush and silver mining in Mexico and Bolivia, but the op-ed unfriendly fact remains that the average estimate of the annual natural flux is 1,230 tonnes larger than the average of the antropogenic flux estimates : geochemistry happens.

  8. Re- Comment by Russell — 1 Apr 2013 @ 2:55 PM

    I am compelled to inform you that Jim Larsen is also in denial of Easter bunny abuse.

    Steve

  9. 107 Russell,

    Thanks for the hint, but I’m a tad old to hunt for Easter eggs. I tried to get you to post a direct link and easy instructions or maybe even a quote, but you still hide behind words without backing. So, yep, I’d love to engage you in your wild claim, but you STILL refuse to provide any information.

    As to my looking at the charts and whatnot, I abide by an absolute no-cherry-picking rule. Either I accept the “opponent’s” data, or I look at data not chosen for values. Thus, I posted the FIRST column and perused the others to see if it was an outlier. Since you’re saying that data is flawed even though it matches every other source I found, well, go for it kid. Show us the REAL data, including links and quotes. After all, if I ain’t smart enough to find this Cherry in a haystack, surely others will fail as well. Enlighten us.

    At least some information, please. Thanks.

    Hopefully my next post will begin with, “Well, lookie there!”

  10. 108 Steve Fish, I plead the 5th, and to insinuate that has anything to do with my denial, well, that’s unconstitutional.

  11. 109:

    There is hope if you can get the level of your cherry-finding up to the level of your cherry picking.

  12. Re- Comment by Jim Larsen — 2 Apr 2013 @ 1:11 PM

    I presume you have checked out Russell’s web site. If not, you can learn the truth about who ate the Easter bunny by clicking his name.

    Steve

  13. Getting back to the original topic, L. A. Times article
    “Climate change will increase extreme precipitation levels”
    http://www.latimes.com/news/science/sciencenow/la-sci-sn-climate-change-extreme-precipitation-20130404,0,125887.story

    One of the commenters points out the U.S. Climate Extremes Index (CEI) pages
    http://www.ncdc.noaa.gov/extremes/cei/graph/4/01-12 and wonders whether somebody has tried to determine correlations between extreme precipitation for example and temperature. Any takers?

  15. Thanks, sidd.

    I was especially looking for the correlation (and presumably causation) relationship of increased temperatures causing extreme precipitation, but that may well need some very detailed looking at what was happening just before/upwind of each particular extreme precipitation event.

  16. GEOPHYSICAL RESEARCH LETTERS, VOL. 39, L17707, doi:10.1029/2012GL052762, 2012, How much do precipitation extremes change in a warming climate?
    Chein-Jung Shiu, Shaw Chen Liu, Congbin Fu, Aiguo Dai, and Ying Sun
    “Daily data from reanalyses of the European Centre for Medium-Range Weather Forecasts (ECMWF) and the National Centers for Environmental Prediction (NCEP) are analyzed to study changes in precipitation intensity with respect to global mean temperature. The results are in good agreement with those derived from the Global Precipitation Climatology Project (GPCP) data by Liu et al. (2009), providing an independent verification for large changes in the precipitation extremes: about 100% increase for the annual top 10% heavy precipitation and about 20% decrease for the light and moderate precipitation for one degree warming in the global temperature.”

  17. Re Comments above on Precipitation

    I think it’s actually a lot easier to understand changes in the extreme precipitation events than it mean changes (contrast this to the robustness of global temperature predictions for the mean vs. extreme events).

    For extreme precipitation events, the upper bound on atmospheric water vapor in regions of convergence plays a significant role (I believe Issac Held has a post on this). This is all well-defined by the Clausius-Clapeyron equation. In contrast, Clausius-Clapeyron doesn’t tell you much about mean changes in rainfall because precipitation is generally energetically limited rather than moisture limited. That makes it critical to understand the energy budgets of the surface or troposphere, including the temperature differential between the surface and boundary layer.

    In fact, there’s very little use in speaking of a precipitation-temperature slope, dP/dT, without a detailed consideration of the forcing agents involved, etc. Precipitation can very well decline in a warming climate, in contrast to the column water vapor amount, which is virtually always monotonically increasing. The latter, I believe, will be more relevant when thinking about the (extreme) tail end of a PDF of precipitation events.