The relationship between rainfall, groundwater, evaporation and transpiration, vegetation, bodies of water, animal distribution, agriculture, humans, and atmospheric conditions (not to mention oceanic factors and topography) underlie many different realms of academia and policy. Almost nothing I’ve ever done in my anthropological research didn’t include the hydrologic cycle, climate, and related issues. The weather weirding we are currently watching across the globe, including the current heavy rains and tornadoes, are part of this, and the long lived California Drought, the one that ended just recently, is as well.
In Drought: An Interdisciplinary Perspective, Cook looks at the dry end of the spectrum of the hydrologic cycle, but in so doing, he really has to cover the basics of rain related climate. There is math, and there is complicated science, in this book, but all of the material presented here is accessible to anyone who wishes to learn. If you are interested in climate change or agriculture, or paleoclimate, or any of that, Cook’s book is an essential reference, filling a gap that exists in the available range of current public-facing serious science books.
Cook covers the hydrologic cycle and the relationship between the hydrologic cycle and climatology. He defines the sometimes confusing concepts and measurements known as “drought” in a non-confusing and detailed way. I’ve found that in many discussions of drought, self defined experts who also happen to be climate change deniers tend to talk past (or over or around) others, making it difficult for the average non-expert to avoid frustration. Cook will arm you with the knowledge to stand up to such shenanigans!
Cook covers drought in the Holocene, and the relationship between climate change and drought. He provides two key detailed case studies (the American dust bowl, and droughts in the Sahel of Africa). He covers landscape degradation and desertification, and irrigation.
Ben Cook is a research scientist at NASA-Goddard Institute for Space Studies and the Lamont-Doherty Earth Observatory of Columbia University, and he teaches at Columbia’s School of Professional Studies.
I have been discussing on this blog for a few years not the problem of quasi-resonant amplification (QRA) of the jet stream. Let me quickly review what that is, then tell you about the new research.
The Earth is encircled by giant twisting donuts of air. The two main donuts lie side by side along the equator. Air warmed at the point where the sun is strongest (a climatological equator that moves north and south with the seasons) rises. It traverses, at altitude, either north or south, towards the polls, then drops and then circles back towards the equator. This drives wetness at the equator as moist air hits cold air aloft and thunderstorms are everywhere.
These primary giant twisting donuts, called Hadley Cells, set up a second set of twisting donuts to the north and south. These donuts, called mid-latitude cells, tend to cause a dry zone to form. Look at a map of the planet, and you can trace the dry zone across the northern hemisphere from the deserts of Central Asia, to the deserts of the US Southwest. In the south, the deserts of Namibia, Botswana and South Africa line up with dry regions of South America and, pretty much all of Australia.
There is a third cell, the Polar cell, north and south of the mid latitude cells.
These cells, as they move around the spinning earth, are the trade winds. Near junctures of the cells, at latitude, air molecules face an interesting mathematical problem. Air pressure, temperature, cell-driven winds, and all the various factors set up a situation where those air molecules sitting between the upper parts of the cells are supposed to be somewhere where they are not, pretty much all the time. In order to solve that problem, the air has to move very rapidly in one direction. This is a bit like nature abhorring a vacuum, large scale. That rapidly moving river of air is the jet stream.
A combination of trade wind effects and the jet stream tends to move storm systems around the planet in the mid latitudes. Under pre-climate change conditions, a low pressure system might ride along just south of the Jet Stream, moving across the planet at a few tens of km an hour, bringing rain followed by fair weather. But if the jet stream either slows or changes direction somewhat, that conveyor belt effect can get kinked up, and the low pressure system can sit in a giant meteorological kink, causing a large region to experience wet conditions for days or weeks at a time. Meanwhile, on the other side of the jet stream, in the counter-kink that a curved jet stream might cause, you can get a stalled high pressure system bringing dry conditions for longer than normal, causing what meteorologist Paul Douglas calls a “flash drought.”
Go back to the beginning a second. This entire process is controlled by the global process of heat accumulated in abundance at the equator moving to the north and south poles. But in recent years, the arctic has warmed considerably. Lack of snow cover in northern Canada and Siberia, loss of sea ice, and, probably, darkening of glacial ice in Greenland, combine to cause the Arctic to warm to a much greater degree than the rest of the planet.
This is a little like putting your refrigerator too close to the wall and building a cabinet around it without proper ventilation. The heat pump that runs your refrigerator will stop working. The behavior of the giant twisting donuts and the jet streams changes.
What occurs is this: The jet stream gets wavy, and that waviness can form a standing wave, like a swirl you see in a running brook that sits in one place because of an underwater obstruction like a rock or log. The wave, in a sense, resonates with the circumference of the earth, so you get a regular number of waves around the planet, and they tend to move only very slowly, or not at all, for months at a time.
There are two phenomena that have caused the plethora of wild and wicked weather we have been experiencing across the globe for the last five or six years. One is the increase in strength and possibly frequency of various storm systems as a nearly direct effect of warming. The other is this QRA system causing major weather patterns to pan out abnormally.
These two problems can interrelate, by the way, but that is a subject of a different essay, perhaps.
The result of quasi-resonant waves? The California drought, massive multi day rainfall events in Calgary, Boulder, Minnesota, China, Japan, Mediterranean Europe, and on and on and on.
Two questions arise from the research showing this effect. One: is it real, is there really a QRA effect? Two: will this persist, get worse, or get better, over time?
The answer to the first question has been getting more and more solid with the publication of research paper after research paper. There isn’t any longer a doubt, in my view, that this phenomenon is for real and seroius. The second question is harder. The paper that came out today on this topic says that the degree of extra warming in the Arctic is probably the biggest factor affecting the future of QRA effects. The research also suggest that it could get worse and it could persist. But there still is some uncertainty.
We find that the incidence of QRA events would likely continue to increase at the same rate it has in recent decades if we continue to simply add carbon dioxide to the atmosphere. But there’s a catch: The future emissions scenarios used in making future climate projections must also account for factors other than greenhouse gases. Historically, for example, the use of old coal technology that predates the clean air acts produced sulphur dioxide gas which escapes into the atmosphere where it reacts with other atmospheric constituents to form what are known as aerosols.
These aerosols caused acid rain and other environmental problems in the U.S. before factories in the 1970s were required to install “scrubbers” to remove the sulphur dioxide before it leaves factory smokestacks. These aerosols also reflect incoming sunlight and so have a cooling effect on the surface in the industrial middle-latitudes where they are produced. Some countries, like China, are still engaged in the older, dirtier-form of coal burning. If we continue with business-as-usual burning of fossil fuels, but countries like China transition to more modern “cleaner” coal burning to avoid air pollution problems, we are likely to see a substantial drop in aerosols over the next half century. Such an assumption is made in the Intergovernmental Panel on Climate Change (IPCC)’s “RCP 8.5” scenario—basically, a “business as usual” future emissions scenario which results in more than a tripling of carbon dioxide concentrations relative to pre-industrial levels (280 parts per million) and roughly 4-5C (7-9F) of planetary warming by the end of the century.
As a result, the projected disappearance of cooling aerosols in the decades ahead produces an especially large amount of warming in middle-latitudes in summer (when there is the most incoming sunlight to begin with, and, thus, the most sunlight to reflect back to space). Averaged across the various IPCC climate models there is even more warming in mid-latitudes than in the Arctic—in other words, the opposite of Arctic Amplification i.e. Arctic De-amplification (see Figure below). Later in the century after the aerosols disappear greenhouse warming once again dominates and we again see an increase in QRA events.
Author Michael Mann notes, “Most stationary jet stream disturbances will dissipate over time. However, under certain circumstances the wave disturbance is effectively constrained by an atmospheric wave guide, something similar to the way a coaxial cable guides a television signal. Disturbances then cannot easily dissipate and very large amplitude swings in the jet stream north and south can remain in place as it rounds the globe.”
From the abstract of the original paper:
Persistent episodes of extreme weather in the Northern Hemisphere summer have been associated with high-amplitude quasi-stationary atmospheric Rossby waves, with zonal wave numbers 6 to 8 resulting from the phenomenon of quasi-resonant amplification (QRA). A fingerprint for the occurrence of QRA can be defined in terms of the zonally averaged surface temperature field. Examining state-of-the-art [Coupled Model Intercomparison Project Phase 5 (CMIP5)] climate model projections, we find that QRA events are likely to increase by ~50% this century under business-as-usual carbon emissions, but there is considerable variation among climate models. Some predict a near tripling of QRA events by the end of the century, while others predict a potential decrease. Models with amplified Arctic warming yield the most pronounced increase in QRA events. The projections are strongly dependent on assumptions regarding the nature of changes in radiative forcing associated with anthropogenic aerosols over the next century. One implication of our findings is that a reduction in midlatitude aerosol loading could actually lead to Arctic de-amplification this century, ameliorating potential increases in persistent extreme weather events.
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.
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.
…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.
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.
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.
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.
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:
Hot Whopper puts this in some context and adds some other sources, here.
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.
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.
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.
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 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?
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.
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.
It appears that there is going to be a bacon shortage. It is estimated that the total amount (in poundage, I assume) of swine that will be produced next year will be several percent, about 10% most likely, less than expected. It is said that there will be an approximate doubling of the cost of pork production, not necessarily doubling the cost of bacon and other products at the consumer end, but certainly squeezing the farmers and raising costs in the grocery store significantly. Presumably this will mean a shortage of all pork products, and quite a few things are made from swine. Why the focus on bacon? Obviously, because without bacon, we will not be able to make BLT’s, and other fine foods, or put crushed bacon on our otherwise perfectly healthy salads.
I’d like to give you a very small selection of references and discussions about the link between global warming and drought.
Global warming probably has two major effects. First, more moisture gets into the atmosphere because warmer air passing over the oceans can take in more water. This can cause more rain and possibly more severe storms and flooding. But the atmospheric system also changes in another way. The hydraulic cycle, as it is called, intensified in both directions, wet and dry. If you live on the East Coast of the US and you move to where I live in the upper Midwest, you’ll get a special appreciation of this. Rain on the East Coast comes in thunderstorms now and then, but a lot of the rain comes from big wet air masses linked to the ocean. In Boston it can rain for a few days off and on but mostly on, with an inch off rain falling over a long period of time. But here in the Midwest, that almost never happens. Instead, it’s not raining, then this big scary storm comes and dumps a whole pile of rain on you, then it moves on. In between storms it can be dry vor many days. The Midwestern storms come from warm air masses passing over the Gulf of Mexico and moving north (then turning “right” at some point) with contributions from elsewhere. It is more intensified hydrological system, with a lot of variation. That is a min-model (albeit a pretty inexact one) for shifting to a warmer planet. Keep in mind that between rain storms, warmer air takes moisture out of the local system (to dump it in a storm somewhere else). Climate experts generally agree that a warmer world will have more severe storms, though which storms will be more severe and in what way is not clear, and drought. Lots of that. Continue reading What is the link between global warming and drought?→