Very substantial subject for the long-term policy decisions. I agree with the insufficient information on local weather changes and also the importance to increase our knowledge.
But isn’t it the time for us to prepare both “adaptation” and “mitigation”? Overstressing the uncertainty would postpone our decision and make our effort “too late”.
It seems to me that the available knowledge today is not sufficient to evaluate the cost-benefit precisely, but enough to give the priority of our options. “No act” is already deleted from the list.
I think “both” is is the key word here. Uncertainty is not an obstacle the way I see it, and we can include that in planning – that is what is done in all risk analysis. Uncertainty is everywwhere, and we deal with it all the time. But that doesn’t stop us… -rasmus
AFAIK the UK government is planning adaptation and mitigation. Although my impression is that adaptation policies are probably more enthusiastically adopted because they are politically easier to sell and can be financed via short term budgets that the democratic process can handle.
From what I can make out, in the change from a Labour government to a largely Tory coalition (right wing), ‘green’ policies have remained intact. Especially when compared to the cuts in many areas. Something for American politicians to learn from?
A very interesting and timely article. One issue I have is that in any risk mitigation exercise, the first essential step is to bound the risks. If you cannot bound the risks, you cannot allocate resources effectively. Unfortunately, there are many factors that preclude an effective bound on the risks–ranging from uncertainties in downscaling to more fundamental issues such as the uncertainty of climate sensitivity. The consequences of climate change rise dramatically with sensitivity, so unfortunately the extremes of the sensitivity distribution wind up driving risk calculus, even though most of us don’t believe sensitivity is as high as 6-10 degrees per doubling.
Moreover, the extremes of a distribution will always be the most poorly constrained portion, and looking for trends in the extremes is bound to be an even more fraught proposition.
If faced by a risk calculus in my day job, I would take one look and suggest that avoiding the threat is the only viable option. Unfortunately, humanity appears to have taken that option off the table. We have left ourselves no choice but to design for a very different future we can only dimly glimpse.
Another global indicator that is projected to increase is sea level. I’ve read, in the mainstream media, about various local efforts to plan for sea level rise but these articles only mention the global sea level rise estimates. My question is do scientists have reasonable estimates of how level sea rise will be distributed? If so, is this information being used?
I have used this to illustrate the seriousness of the climate change threat, but I am a little uncomfortable about the methodology. As I understand it, he combined regional projections of rainfall with regional projections of temperature, to obtain regional projections of PDSI, using the means of multiple runs. That would seem to create pretty wide error bars. Still, I suppose it it useful to know the “mean” PDSI produced by the two means of rainfall and temperature. Sorry to be so vague about this – it is because my understanding is so vague.
The problem is not WHETHER we should do something, but WHAT we should do. If sea level rise is going to be manageable, we can focus efforts on barriers, improved wetlands, etc. If not, we should focus on evacuating low-lying areas.
If increased drought were to be a minor threat, we might focus on improved water retention and farming techniques in existing agricultural areas. If it is as serious or moreso than thought, we will have to develop entirely new food crops.
Severe weather, river flooding, heat waves, drought, sea level rise, increased pests and disease and on and on–we cannot defend against the worst case for every threat. Without a bound on the consequences, we don’t know where to focus our limited resources.
The discussion is cautious and tries to account for uncertainties, e.g. by looking at an ensemble of 22 computer climate models and a comprehensive index of drought conditions. The analysis also follows the advice in the IPCC Good-Practice-Guidance-Paper on using climate model results: the local climate change scenarios should be based on (i) historical change, (ii) process change (e.g. changes in the driving circulation), (iii) global climate change projected by GCMs, and (iv) downscaled projected change. We do have some information about historical change and we do have a physical picture of process changes. In the end, there are lots of uncertainties, but studies like these go a long way to elucidate the situation – according to the best information that we have. -rasmus
“Adaptation” normally means evolution by natural selection. Evolution by natural selection means that new mutations are selected and the prior species average dies out. Natural selection is always accomplished by mass death. Oreskes, Stainforth and Smith are misusing the word “Adaptation.”
People “accentuate the positive” in adaptation, and emphasize the growth of the new or modified species. That is fine when it was a long time ago and not us. In our own case, Oreskes, Stainforth and Smith are assuming that no natural selection need take place. I suggest that they invent a new word that means what they want to say. “Adaptation” isn’t it.
I agree with Ray Ladbury, the key problem here is to do a decent risk assessment. When you are doing risk management you prioritize risks by multiplying their probability with there expected consequence. In the case of climate change, risks are largely loaded on the worst case hypothesis. This as been supported by a few economics analysis.
Hence, the rational think to do would be to plan for those extreme risks. But a this point, the unknown is very large, which means the worst case is really really bad. So bad that is psychologically unpalatable. Any experience engineer will tells you that in such situation most managers with have a tendency to reject the risk estimation since it is too pessimistic.
We all know what is the typical consequence of such behaviour.
Historically, past sea level changes analyzed by NOAA have shown significant varations in measurement. The highest observed changes have been in the Japanese and Phillipine islands. The greatest sea level decreases have occured in and around Scandinavia. The two areas will proabaly continue to lead due to glacial rebound and tectonic movement.
Other areas of pronounced increases include the east coast of North America and New Zealand, while decreases have been measured throughtout Alaska.
The Pacific Islands need each be considered individually due to different factors affecting each island. Islands such as Guam and Tuvalu have actually shown a decrease in sea level, while others such as Wake, American Samoa, and Tonga have shown shown large increases.
How this information is being utilized, I cannot say. Hope this helps.
In looking at a wide range of possibilities and attempting to weigh uncertainty with preparedness verses cost, I think that the a careful consideration of the precautionary principle provides a basis for adaptation on a regional basis.
Farming practice, localizing food production, flood management, extreme snow events, water management, sewage handling are all important infrastructure areas of consideration. In some of these cases, adaptation in efficiency of handling would benefit us whether we had climate change or not.
That is, in my mind, a good basis for some decision processes. ID deficiency in areas where there is overlap weighed against potential risks to cost/benefit, and focus funding in those areas.
The US Navy Arctic model (Maslowski) sets a different time line. The Navy model at first looks like a simple extrapolation of the decline of ice volume, but there is a supercomputer model behind it – not a global model but a more detailed model of just the Arctic region. Ocean heat is the main driver of ice reduction for sea ice and glaciers that run to the sea. If the Naval model turns out to be right, it effects all the other projections. This ought to be part of bounding the risk. Is there any reason why the Naval model is not included in multimodel studies?
Ray Ladbury: If sea level rise is going to be manageable, we can focus efforts on barriers, improved wetlands, etc.
The total miles of coastline is daunting.
Comment by Pete Dunkelberg — 7 Mar 2011 @ 12:09 PM
This is really the first time in human history that we have had the opportunity to proactively adapt to future changes. The problem is that downscaled information is never going to have all the answers, yet, there persists this idea that once we have higher-resolution information we will have what we need to act on adaptation. This is simply untrue. Especially when you start looking at variables like extreme rainfall, the projected amounts completely depend upon the downscaling technique and the climate model. That’s not to say downscaling cannot be useful, but sometimes I think it has been oversold to decision-makers and we need to be drawing more heavily on the social sciences to work out how to make decisions that will robust under a range of possible futures.
Rasmus – nice post. I’ve been browsing the Google Earth trajectories, and one puzzle arises (which I can’t resolve as I haven’t gotten to the paywalled paper). A spot check of many of the A1B station scenarios (Red Lodge, Berkeley, Salamanca, Pusan, Sydney, etc.) shows that the rate of increase of temp slows a lot at the end of the century. I don’t recall seeing that in global A1B scenarios (e.g. http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch10s10-5-3.html ). Is that the real outcome, or is it just an artifact of looking at too few stations, or perhaps a smoothing boundary assumption? – Tom
Excuse my ignorance, but are there ways to usefully combine climate models and weather models? Say, for example, use GCM’s to estimate an increase in humidity, then run a weather forecasting model allowing for that increased humidity. Would that return any useful info? I’m sure someone’s thought of this already!
Comment by One Anonymous Bloke — 7 Mar 2011 @ 12:32 PM
The biggest risk in preparing for climate change has nothing to do with climate. The biggest risk is economic. We can predict climate with modest certainty, but we can’t predict future economies and technologies at all (note the unpredicted nature of both the recent economic meltdown and the digital revolution). Given infinite resources and infinite knowledge of future technological developments, we could prepare effectively. But we have neither.
If we prepare for climate extremes by employing high cost / inefficient technologies immediately and lower cost / more efficient technologies emerge in the near future, we risk a significant economic setback – which will appear more pronounced if climate extremes do not materialize. OTOH, if we do nothing and the extremes do materialize, we risk the same result.
We should think of climate change mitigation as an investment for which the fair price and future yield is uncertain but presumed positive. To get the most out of our limited resources, we average in.
Spend heavily on the currently most economically/GHG efficient mitigation technologies (IMO, hybrid transpo and nat gas/nuke electrical gen), and increasingly phase out the most GHG inefficient technologies over time (coal). Spend modestly on implementing barely economically efficient technologies (wind), and sparingly on economically inefficient technologies (solar), but commit research dollars to all promising but economically inefficient technologies (solar, wind, tidal etc). Adjust priorities as technological change demands.
Loosely relevant, but the UK government has been reported to be giving higher priority to get the UK off oil dependency for its energy needs as a matter of national urgency, not provoked by climate change but by ongoing events in the Middle East. It includes getting us on a low-carbon pathway, promoting a national infrastructure for electric vehicles, deadlines for building low-carbon homes, Greenpeace being asked to monitor progress. China is also used as an example of what’s coming in terms of alternative energy sources.
I think care is needed in claiming that one event can’t be attributed to warming. The example of hurricanes is a good one for saying this. One strong one is neither here nor there in terms of warming. But what of an extended record heat wave? It is one event because we call it so, yet fractional attribution may be possible. What of a multi-decade drought? Again, it is one event because we call it so, but now it is stretching into a timescale over which climate is measured.
It can lead to confusion if the possibility of attribution is dismissed too reflexively.
Came across this story today, and it seems pretty on-point for this thread. Won’t have a chance today to check out the study itself; perhaps someone else will want to bird-dog it for us?
At any rate, Feng et al. say in a new “Climate Dynamics” study that “By the last decades of this century, only small, scattered patches of tundra are expected to remain along the mainland Arctic coast,” replaced by boreal woodland. (Although tundra should persist in the Arctic archipelago and may expand in Greenland as the ice cap shrinks.)
Tom Fid: Good question. I haven’t got to the bottom of this yet, but there are several plausible explanations: (i) some of the simulations in the downloaded models from the CMIP3 ensemble stop early, affecting the whole envelope of results, (ii) the use of common EOFs fail to capture large-scale temperature patters that are too different from the past. So my guess is that it’s a likely artifact. -rasmus
“a decent risk assessment”:
We already have a decent risk assessment. The biggest risk is NOT economic. Sea level rise is irrelevant to the greatest risk. Our own Bart Levenson told us everything we need to know. The greatest risk is the collapse of agriculture due to drought.
Without agriculture, there is no civilization. Without civilization, there is no need for port cities on the seacoast. Without agriculture, there will be no people to populate the cities. It seems to me that at least some of the commenters are in psychological denial of the biggest risk. Sorry, but it is time to concentrate on the biggest risk and forget about minor details like sea level.
“downscaling”: Lack of downscaling gives denialists one more weapon since Dr. Aiguo Dai’s maps show my location as dry in 2008 when we had 3 floods instead of 1. We do not need downscaling to know what to do. What to do is mitigation. We need downscaling to get the present weather right so that denialists will not have this weapon.
Thank you to those who elsewhere provided links to the recent issue of the Philosophical Transactions of the Royal Society. One of the articles in that issue presents what I found to be an helpful discussion about adaptation strategies.
From the abstract: “. . . In this paper, we show how complexity and uncertainty can be reduced by a systematic approach to categorizing the interactions between decision lifetime, the type of uncertainty in the relevant drivers of change and the nature of adaptation response options. We synthesize a number of issues previously raised in the literature to link the categories of interactions to a variety of risk-management strategies and tactics. Such application could help to break down some barriers to adaptation and both simplify and better target adaptation decision-making. The approach needs to be tested and adopted rapidly.”
Adaptation is a myth. We are having some theoretical discussion that has no connection with actual future events, and human responses to it. People will be on the move on a massive scale and that’s about the only adaptive measure that I see happening long-term. But let’s just assume that adaptation is real. What are the options? Turning up your AC, learning how to get out of your car quickly in case of a flash flood; stacking up on canned goods when crops fail; getting to a shelter quickly when that tornado strikes in places where it’s never struck before? I have heard people talking about growing vegetables in their basements. I can’t even believe that anyone would make such a suggestion. Who even came up with the notion of adaptation or resilient communities in the first place? It’s horridly cynical at best (some of us will survive because they can turn up the AC) and dangerously stupid at worst. Someone please debunk the whole notion since that’s apparently necessary.
Rasmus, thank you for your thoughtful, very helpful response (10). It gives me confidence to move ahead with Dai’s study. If his results are even close to being right, we are likely to have great trouble producing enough food by mid-century.
I share your judgment about priorities, though you could include some other measures.
My list includes much of yours, but I also see (1)reason to look further into stimulating plankton growth in the oceans, and(2)establishing standing forests with water made available by re-distribution of water on a continental basis, at least in North America. (3)Continuing with improvements in insulation has significant quantitive potential. Also of potential large magnitude benefit, is(3)changing away from an electric power generating system where power plants are located in remote areas but are connected by a grid, whereby this practice has caused a massive energy wasting establishment. We also might note that motor vehicles, these being both cars and trucks are second only to electric power generation when it comes to CO2, and these could be vastly improved by rejecting standard automotive practice and insist that cars be aerodynamically efficient like well known airships.
I endorse 39 Lisa McFadden. What is happening all across the north coast of Africa is stage 1 of GW adaptation, accepting merriam-webster. Notice that Europeans are keeping the Africans out, so far without violence. That will change. Adaptation means killing the excess population, just like in Rwanda. Mitigation is the only reasonable thing to do, but it has to start several decades in the past.
Lisa @ 39 Who even came up with the notion of adaptation or resilient communities in the first place? It’s horridly cynical at best….
Very good point. We personally (unless some real youngsters are reading this) are not personally the ones who will have to “adapt” to high heat, drought and flood and low resources of all sorts.
Do you think maybe we should stop burning carbon like there’s no next generation?
Comment by Pete Dunkelberg — 7 Mar 2011 @ 10:07 PM
Jimster @ 23, No to natural gas. It is methane and it leaks. Recalculate your economic efficiency of energy sources. The official cost is based on considering some “external” costs, but not the Big One, or else fossil fuel would be priced out of the market by a mile. Compute real costs and put the upfront money into non-carbon power. If nuclear, use thorium molten salt reactors to avoid excessive water use. And by the way outlaw watering lawns. Adapt! Get over your grass!
Instead: 1) mandate net metering everywhere. (meaning those with solar power can sell power to the grid as well as buy it). Make homeowners aware that with solar on the roof to power an electric car in addition to the lights they come out ahead in time. Apartment dwellers,if they object to the up front cost of power, can move closer to work. There’s adaptation for you. 2) Mandate bike racks in addition to handicap parking. Make everyone healthier. Adapt!
3) leave reduced carbon in the ground.
Edward, I had somehdow missed your 30. I doubt that Dai would defend as predictions the results of his analysis for a specific point on earth in a particular year. Rather, I think it is the maps showing decadal averages that are most meaningful. But, in any case, I quite agree that the collapse of agriculture is the great threat, and we should place a high priority on genetic engineering of crops for higher temperatures and drought. There is no assurance that this would be successful. You just can’t develop corn that will grow in the Sahara.
While not the greatest threat, sea level rise will still a big problem, because of the demands adaptation to it will place on resources. We may simply have so many big problems simultaneously that they overwhelm the capacity of civilization to adapt.
Pete Dunkelberg wrote: “We personally (unless some real youngsters are reading this) are not personally the ones who will have to ‘adapt’ to high heat, drought and flood and low resources of all sorts.”
“We personally” are already having to adapt to drought-driven crop failures in the world’s major wheat-exporting nations (Russia, China, Australia) and there is no reason to believe that a comparably devastating drought won’t afflict North America as well, within the lifetimes of even the “real oldsters” reading this blog.
I’m almost sixty. I fully expect to see chronic, world-wide famine settle in, within my lifetime. And perhaps much worse.
Lisa McFadden wrote: “Who even came up with the notion of adaptation or resilient communities in the first place? It’s horridly cynical at best …”
I disagree. Resilient communities, based on locally-generated solar and wind-generated electricity and local sustainable organic agriculture, are the way that human beings will live in the future — if we are to have a future. And of course, they represent not only adaptation but mitigation as well.
Lisa McFadden wrote: “Who even came up with the notion of adaptation or resilient communities in the first place? It’s horridly cynical at best …”
I also disagree with this conclusion. What do we want un-resilient communities? We can either give up or do everything in our power to make sure that the most possible local communities have the best possible chance of surviving the coming collapse. Hope is not cynical. Adapting agriculture to local conditions, building to handle increased heat without air conditioning are just of the few changes we need to make.
“If we prepare for climate extremes by employing high cost / inefficient technologies immediately and lower cost / more efficient technologies emerge in the near future, we risk a significant economic setback”
History shows that whatever technology is available is used and then when something new comes along, it gradually replaces the the older technology. In fact you actually describe the process quite well!
So why the panic??!
Oh wait a minute, also throughout history there has been resistance to change, with claims that technology would be bad for health, to costly etc.
Meanwhile many decades after it was built the over engineered Forth bridge is still in use, people are still travelling by train despite the initial worries that the speed would make people faint.
And those expensive and inefficient automobiles are now more efficient and cheaper!
See the pattern?
It’s the one you describe and it has been happening since the start of the industrial revolution.
A few people have refered to Dai’s (and by extension Barton’s) predictions about coming drought. These predictions are based on calculations which have shown that many areas having shown an increase in aridity at the same time that rainfall has increased. The predictions are based on a temperature increase resulting in increased evaporation of the increased rainfall. The areas that have supposedly become more arid (based on Dai’s calculations) have not become so. I, for one, am questioning those calculations as they do not correspond to the observed data.
To paraphrase Mark Twain, “News of the death of civilization due to agricultural decline has been greatly exaggerated.”
And yet, we are seeing food insecurity begin to become a fact of life again in much of the world. It was in fact one of the causes of the revolts in Tunisia and Egypt. Now why do you think that is? Oh, and what color is the sky on your world?
Well, that’s kind of the point, isn’t it? Despite production and yield being maximized, supply still isn’t meeting demand–and production and yeild are being propped up by unsustainable reliance on petroleum and aquifer depletion. And yet, guys like Dan H. and you repeatedly assume there’s nothing to worry about and everything’s fine. In reality, we are doing irreparable damage to the planet’s ability to support us every single day.
> grain production
He’s posting a talking point, same one was used at the hearing. No cites.
I posted links refuting the same handwaving assertion that everything is good and getting better as it gets warmer, in the live chat thread yesterday.
“the history and hype surrounding corn yields has one staggering asterisk: The very best farms, blessed with the best weather and land, have posted the same yields for at least 20 years — suggesting they have reached the limit of what the corn plant can produce.” http://www.startribune.com/business/46495542.html?elr=KArks7PYDiaK7DUHPYDiaK7DUiD3aPc:_Yyc:aUUr MATT McKINNEY, Star Tribune June 3, 2009 – 10:44 AM”
Dr. Field, in the hearing, provided data on temperature thresholds already reached causing decline in several important grains, and several more have thresholds that are very close. That’s the peak temperatures that knock down the yield of the crop.
SA @ 50, Larry S @ 51, try to get Lisa McFadden’s @40 point. Of course no one is against resilient communities. What is cynical in her meaning is destroying the environment and saying future people should just be “resilient” instead of us destroying less.
Link 1 didn’t work and I don’t have time to go down to the county data but Iowa yields grew at a 2.2% anually averaged over the last 10 years. http://www.extension.iastate.edu/agdm/crops/pdf/a1-12.pdf
But the point is important and there maybe a time when we reach the limits of technology. We run the greatest danger of this as we employ the latest tech. However there is a lot of the world that doesn’t use the latest and best and can see real gains in yields
As to your chart, it is 15 years out of date and irrelevent anyway.
At 55 Jack Ballard says “Given that world grain production is at all time highs and yields are too”
Miffed at being asked for his sources, at 60 he gives cites, which actually show that the most current harvest is in fact lower than the all time high on every measure including stocks on hand, both in the U.S. and world wide.
Try again Jack, we see your level of comprehension now concerning “playing with numbers”.
November 1, 2010, doi: 10.1073/pnas.1011078107
PNAS November 16, 2010 vol. 107 no. 46 19645-19648
Trading carbon for food: Global comparison of carbon stocks vs. crop yields on agricultural land
“… Here, we present a spatially explicit global analysis of tradeoffs between carbon stocks and current crop yields. The difference among regions is striking. For example, for each unit of land cleared, the tropics lose nearly two times as much carbon … and produce less than one-half the annual crop yield compared with temperate regions …”
I’m used to tastier troll bait than that Better work on your technique
That is well known amoung farming circles, of course they don’t talk about carbon, they put it in terms of organic matter.
and yeah land in the tropics don’t have much and it is gone fast. With out really careful stewardship tropical land can turn sterile in a short while. It is one of the reasons that we don’t list tropical areas among our major crop producers.
Rain leeches out the nutrients fast. with the increased water vapor in the air from global warming, leeching from excess rain fall may be more of a problem for the future of agriculture than the scary scary drought everywhere worries.
Well, Jack above is basically claiming what’s in the IPCC’s last report, but more recent work suggests the IPCC was optimistic.
“… the relative rates of yield increase for all of the major cereal crops are already declining ….”
Hey, it’s an important area, there’s a good bit of research to read, and sometimes we only do get into talking about it here because somebody like wossname the advocacy scienceist, or Jack above, post talking points that someone bothers to check into.
How Do We Improve Crop Production in a Warming World?
“… The IPCC projections assume that yield improvements from the latter half of the 20th century will continue into the future; however, based on historical temperature-crop yield relationships, potential ceilings to crop yields, and limitations to expansion of agricultural lands, that assumption may not be sound (Long and Ort, 2010). In fact, the relative rates of yield increase for all of the major cereal crops are already declining (Fischer and Edmeades, 2010).
In a global analysis of crop yields from 1981 to 2002, there was a negative response of wheat, maize, and barley (Hordeum vulgare) yields to rising temperature, costing an estimated $5 billion per year (Lobell and Field, 2007). An analysis of maize and soybean (Glycine max) production in the northern Corn Belt region of the United States found that productivity was adversely affected by rising growing season temperatures from 1976 to 2006 (Kucharik and Serbin, 2008). The response of maize and soybean to temperature is also nonlinear, and the decline in yields above the temperature optimum is significantly steeper than the incline below it (Schlenker and Roberts, 2009). Based on the nonlinearity of the temperature response, U.S. maize and soybean yields were predicted to decrease by 30% to 46% before the end of the century under the IPCC scenario with the slowest warming trend (Schlenker and Roberts, 2009). In addition to these historical trends, record crop yield losses were reported in 2003, when Europe experienced a heat wave with July temperatures up to 6°C above average and annual precipitation 50% below average (Ciais et al., 2005). Such extreme events are not well characterized in the IPCC assessment simulations (Easterling et al., 2007). Therefore, increased global temperatures and more frequent temperature extremes will greatly challenge agriculture in this century. Here, we identify regional priorities and biological targets for adaptation of agriculture to rising temperature. …”
So Hank, where are the charts showing this yield curve going down.
If it is happening we should be seeing it.
Yeah, heat and drought affect yields. And you can cherry pick all you want. But lets see that chart with numbers.
From all the data presented, it is apparent that grain production has increased over the past several decades. All this has occurred during a time of increasing atmospheric CO2, mostly increasing temperatures, and slightly increased precipitation (on average). Of course, there are technological advancements which are difficult to factor into the equation. But based on this data, why are some people predicting a huge future decrease in agricultural production? These conclusions are not supported by the data. In fact, they are contrary to the data. One would expect a continued increase in agricultural output as a result of an increase in CO2, temperature, and precipitation.
Jack Ballard and Dan H.,
Yields have been increasing becuase of increased use of fertilizers and irrigation (much of the water coming from nonrenewable aquifers). This is not sustainable–especially as temperatures increase, as petroleum is depleted and as growing population continues to make ever greater demands. Look at fisheries–declining across the board. Rice-one of the more temperature sensitie grains–has already shown decreasing yields with temparature.
Snide comments aside, your link references a report in PNAS by Welch, et. al. Their conclusions for rice are that “higher minimum temperature reduced yield, whereas higher maximum temperature raised it.” The temperature correlation was confounded by the changes in solar irradiance (clouds). The study also concluded that yields had grown during both the high- and low-yielding seasons, contradicting your statement that rice yields have decreased. Irrigation have have affected these yields as all the studied fields were in “intensely managed irrigated rice farms.”
Granted irrigation, fertilization, and other technological advances have probably resulted in significant yield increases. Possibly so much that any recent temperature effects are masked. However, recent data shows increasing crop yields during the time of greatest temperature increase. On average, global food prices have also decreased during this time. Funny that all crops have increased significantly except for cereals, and yet, t_p_hamilton focuses on this trend.
Recently read an article on African maize production and increasing temperatures. It stated that yield is affected by temperatures in excess of 30C. 30-31C, -1%/day. 32C, -2%/day. Drought, -2%/day. Yields are anticipated to be reduced 20% by 2050 in 2/3 of African growing regions.
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