The 2012 drought in continental US was severe. We talked about it here, including the possibility of a climate-change connection. New paper in the Journal of Climate uses tree rings to assess drought over the last 1000 years in N Amer. In that context, the 2012 drought was far from the worst. Sometimes they have continued for multiple years. So, such things have happened even in non-CO2 perturbed climates, and bear that in mind when things get overstated (it does happen from time to time). So that, along with the fact that tree-ring records are excellent proxies for drought, there's your good news. Obliged to also consider the bad news. N America can get really bad droughts. The same research group found the same thing previously in monsoonal Asia, mostly using the same technique. Thus it is not a stretch to consider that any continent can have multi year megadroughts. Problem is that we are now so many and depend on new water arriving at more or less average rates. Agriculture and thermal power generation, just to name a couple of absolute essentials. The amount you drink is nothing compared to the amount that the food you eat requires. I don't know how we would prepare for such events. I presume that we won't. So, it is another one of those 'trust to luck' situations.
Hey DAS, Guess the climate discussions are kind of lacking these days for some reason. Probably the nuclear political discussions in FHOPol have been distracting. It seems like most of the mid-west and east are currently getting a lot of cold weather and snow. Wonder if that precip will help heal the land?
First we are much more prepared in multi-year drought plagued texas, that we were in the decade without rain in the 40s and 50s. Unfortunately the population is much higher too. The worst drought year has been 2011 in texas, but we are far short from multi-year droughts that have happened. Things that have improved, that may help the rest of the country. Better water management and irrigation, along with wide spread air conditioning (droughts in texas are hot) and an improved grid to pull power from power plants far away if the local ones don't have the water to run as well as more water free power from new wind. 2011 we needed to import electricity from mexico, and truck water to communities that did not have it. Better transportation also allowed easier imports of food from mexico and other states, as a large part of the texas crops were destroyed. What we have not managed well is planting. ENSO prediction let us know before hand that it was likely a drought year, yet water was wasted as well as seed, diesel, and labor on crops that were destroyed. Beter prediction, preparation, and drought resistant crops would help. Part of it is the rules. Farmers get reinbursed by the federal government for crops destroyed by droughts, but I don't think they get money if they don't plant. Wild fires also were not controlled well in that year, and this is a problem in many states.
Step one is to get educated on what can happen and why. Just the fact we now research such things and look for underlying causes is a huge and critical step to doing something smart. So yes, our preparations may be lacking, but even the most primitive forecasting suddenly motivates a great many people to get smart. I know of no farmer that ignores useable forecasting data. I know also, that with a lack of forecasting data, farmers plant for the highest payoff crops assuming ideal conditions. Step two is to process the forecasting data. No need to worry extensively about government intervention to make this happen. Most farmers are smarter than the government. (That causes problems as well as provides solutions! Farmers are much better at manipulating governments than mother nature.) Step three is to step back and watch. The first lesson is the hard one. It is also the most effective one.
Recently they are saying Monarch butterflies had a big kill-off this year, I heard due to the combination of the Texas drought combined with some pesticides used in Texas. I don't know if this means the Monarch butterflies are gone forever, or what? Regarding drought history, this Fall we visited the Jamestown settlement in Virginia...where it all started for us. They said there was a terrible drought in Virginia those early 1600 years, which lead to unbelievable death rate among the settlers (bad water in the wells etc). Of course, if the same thing happened today it would be considered incontrovertible proof of AGW.
The milkweed that the butterflies feed on was partially destroyed by the wildfires during the drought of 2011. This has hurt migration. People have told me that the land will recover, but 2012 and 2013 were not good enough weather for this. The lakes and rivers are still low. Someone more knowledgable about the specifics might be able to tell us if the land will recover fast enough for the butterflies. +1
Tree rings contain information about temperature, carbon dioxide, and percipitation. Other proxies can help determine shocks from temperature or low carbon dioxide, so drought shock should be fairly obvious.
Actually tree rings are a muddied proxy for temp ,precipitation and co2. Also a proxy for insect infestation.Not really "excellent" for determining any particular thing.
That's why disciplined research also looks at sedimentation, ice cores, pollen counts, water table variation, vegetation life histories, and every other possible proxy. It's the total combination that we get our information from, not one source. Carbon dating depends upon other information for calibration as just one example.
You probably did not understand my post, or are willfully ignorant on theses matters. In peer review, that happend way after the fact of the paper (we should learn that cherry picking your friends to peer review your paper, doesn't mean it really had proper criticism), we find MBH '98 did not properely account for the affect of other factors than temperature on tree ring growth. Key here is thought to be carbon dioxide in the system. Sensitivity to carbon dioxide and changes in solar radiation may account for the decline, that was hidden with a statistical trick in the paper. We do have a good proxy for global tempeartures and carbon dioxide, that is the ice cores. When used properly with the ice cores tree ring proxies can add some resolution, as the ice cores blur together time. If you are following along then we know carbon dioxide, the problem with the proxy does not change quickly. We also have temperature typically moving in the oposite direction of drought. That is drought normally means less rain, which implies less clouds, less blocking of solar radiation and higher temperatures. Cold and drought reduce the growth and size of the tree ring, which means we can qualitatively separate these things. Definitely with the ice core proxies for temperature, co2, and volcanic erruption taken into account, tree rings provide an excellent proxy for drought.
I am looking for a recent review of dendrochronology. Hows, whys, strengths and weaknesses. Have not found it yet. If someone else has seen one, please let us know. In that search I found this Applications of proxy system modeling in high resolution paleoclimatology Quaternary Science Reviews 76 (2013) 16-28 http://dx.doi.org/10.1016/j.quascirev.2013.05.024 Which is free online (use google scholar to know where). Looks like a good general overview of paleoproxies. When I say ring width is excellent for drought, it is actually based on personal experience. I would go so far as to say trees are more sensitive to drought than anything else, short of extensive defoliation. Sensitivity to T (within ranges that the particular tree species can handle) is much less. There is persuasive evidence that wood is the last thing that trees make. Foliage first, roots second (including root exudation), then flowers and seeds, and if any carbon is left over, expand the stem. From that perspective, annual wood growth is sensitive to trees' overall happiness. Some paleo studies use only trees, and others combine methods as AustinG said (and the cited review also says). When they show concordance, it limits our risk of getting fooled. Using only tree-ring width to get at temperature changes over a narrow range is far from ideal. But for multi-year strong droughts, heck yeah. As I have said before, wordpress sites are generally not available to me, so I cannot directly appreciate Goddard's insights. But I am of the opinion that a real published review of dendrochronology/dendroclimatology would serve the purpose better.
I'll ask Sheppard for this review paper (you can too, just find his email) Dendroclimatology: extracting climate from trees - Sheppard - 2010 - Wiley Interdisciplinary Reviews: Climate Change - Wiley Online Library (that denied access stuff in my link means I don't get a freebie. Nobody's perfect) There is also a 2011 book Dendroclimatology - Springer And Springer would rather that I not mention whether I have access or not
Actually I find that I already gota copy from Sheppard (in 2013 January). Did we talk about it here before? is there interest in doing so?
