In the US, there is only 1 drought 7-years long in the last 60 years and only a half-dozen or so that are 3 or more years long. On top of that, you have a temperature signal that is multi-decadal. It is not possible to mathematically demonstrate whether the frequency or intensity of anything has changed.
Further, you will not find many legitimate scientific studies making general statements of recent events being the result of AGW. What you will increasing find, though, are specific studies of specific recent events that find either (1) evidence and physical explanations for AGW probabilistically contributing to a particular event or (2) the absence of such evidence and physical mechanisms.
>> IS there enough evidecne to conclude that AGW will in the future significantly lessen our crop production?<<
That varies by region and crop, and the conditional probability of future extreme weather events.
>> SO pegminer, Your answer is NO for all, BUT your models tell you it should happen<<
No models say that it should happen before the last half of the 21st century – and the AGW forecasts of changing precipitation patterns and intensity is – and has always been – based on empirical evidence and well-understood properties of atmospheric physics.
The answer to all three is no. The IPCC SREX report acknowledges that the answer to the second is no. Yet many continue to ignore this reality every time there is a hurricane.
Michael Mann has posited more droughts in response to global warming, because it would produce more La-Nina like events. The implication of this is that the models are missing a huge negative feedback. When asked about it, he replied that he agreed, even though the question said 'warming in models is vastly overstated'
In short. No to droughts, no to crops, no to hurricanes, and as for predicting any losses to crop yields in the future... well that depends on your definition of "significant."
http://www.gfdl.noaa.gov/global-warming-...
Here is an analysis on global warming's impact on Atlantic hurricanes by the GFDL, part of the NOAA, which is part of the US dept. of Commerce. In the summary they state that it is premature to say human activity has caused a detectable change in Atlantic hurricanes. However, they counter by saying by the end of the century these storms will likely be more intense by 2-11% and have about a 20% increase in rainfall.
http://phys.org/news/2014-03-climate-cro...
http://www.nature.com/nclimate/journal/v...
In these two links we have a 2014 meta-analysis (and an article about said study) of future crop yields, which will help answer your last question about predicting the future. There is a link to the study so you can read the abstract for yourself. I will be paraphrasing the lead author in saying that crop yields will be lowered by climate change by as soon as 2030 and the year-to-year variability of crop yields will become more and more erratic.
So the models do predict that crop yields will be impacted by climate change. And models are really the best way we have to predict the future.
No. There isn't enough evidence to conclude anything. All you could possibly conclude is that the evidence based on models indicates that warming might increase the possibility of droughts in some places. Notice that alarmists always predict drought in dry areas and more rain in wet areas, etc. Their models are as reliable as North Korean farm futures.
Is there enough evidence that AGW has 'caused' droughts? No. There is, however, enough evidence that AGW has caused warming and there is enough evidence that that warming has affected drought intensity in some areas of the globe.Scientific evidence which you have chosen to ignore and continue arguing as if I am discussing frequency and not intensity as always.
The article you constantly post is the following:
http://www.environmentportal.in/files/fi...
This article calls into question the PDSI and it's reliability in assessing droughts. While, a year later, the following was released:
http://storm.colorado.edu//~whan/ATOC480...
However this is based on PDSI. The article I usually post in response is based on observational satellite data. It specifically states that there has been no changes in droughts over land globally but regional changes have occurred with significant drying patterns in areas current models predict would happen.
http://amir.eng.uci.edu/publications/13_...
This assessment agrees with what you are stating, that there has been no increase in droughts over land, but you have chosen to attack it regardless. It does not use the PDSI but uses meteorological data. The following paper, which you may find interesting, goes into differences of precipitation patterns related to warming sources.
http://iprc.soest.hawaii.edu/users/jylee...
The following is a direct reply to the article you usually post:
http://www.cgd.ucar.edu/cas/Trenberth/we...
I haven't really looked much into crop production.
With hurricanes there is evidence that they will decrease in a warming world, due to increases in wind shear, while increasing in intensity, due to increases in sea surface temperatures. These are, however, based on models, And though the trend is currently occurring, as you have shown and argued before yourself, there is still debate in the area.
ftp://profs.princeton.edu/leo/journals/K...
http://www.ask-force.org/web/Global-Warm...
I'm not a "climate change scientist", but I will contribute an answer.
I am very surprised you think such things are "simple" questions. They might be simple in a thousand years, but teasing out the differences between natural variation and the small but growing signal from global warming over a relatively short time period of observation is really quite difficult. There are certainly people working very hard to do that, but I think they have to use very sophisticated statistics for those purposes. Also, you should understand that these effects will get largre as the warming increases. What's difficult to pull from the noise now may be much easier to see with a 2, 3 or 4 C rise in temperatures, but the consequences of waiting around might be catastrophic.
I think an analogy might be useful here. I don't always work on meteorology and climate, Sometimes I do work in nuclear resonance. If I run a single nuclear resonance experiment, it will generally be impossible to see the resonance signal. The noise will be MUCH smaller than the signal I hope to see. Does that mean the signal is not real? No, of course not. In fact, I may run the experiment a 100,000 times, and then by combining the output from those 100,000 experiments the signal becomes obvious.
We're in a time period where the signal from global warming is just beginning to reach the level of detectability in weather phenomena, but we expect to see it because (1) the physics tells us so and (2) we can run numerical experiments multiple times (but still not as much as we'd like) to build up statistics on what we should expect in the real world. Now we can sit around and say "Oh, there's no evidence that that any of these things are happening" because we can't always prove statistical significance on what we're seeing around us. However, to do so is to ignore relevant information--we may not have an ensemble of identical Earths to gather data from, but what we do have is hundreds of years of physics that we're confident in.
EDIT: My answers were not "no" to any of them, it's not my field. I believe if you go into the literature there will be multiple papers that address these questions written by people that actually study those things. Try looking at the Bulletin of the American Meteorological Society's annual 'State of the Climate" issue for references.
For AGW leading to droughts "without models" you have to be careful--virtually everything in science is a model of one sort or another. Basically we expect that as the temperature gradient between the poles and tropics decreases (due to increased warming near the poles), we will see an increase in the size of the Hadley Cells and their associated dry regions. On the regions that are currently near the poleward border of the cells, they will more often come under the influence of the descending branch, causing extended droughts. In essence those areas are becoming more like the perpetually dry regions that are equatorward of them.
The best the believes can do is if there's an on going drought, then they can find evidence of why it was caused by so-called "global warming". Once a flood happens, then we can find the proof that it too, was caused by so-called "global warming". In fact, so-called "global warming" science is very accurate at finding the cause for something only after it happens.
Anonymous,
Good, then present that conclusive evidence. LMAO, can't wait to see this.
Stubby,
Present the evidence. IFF I cannot attack it based SOLELY on sound scientific reasoning, I will concede that the answers are yes. But I have to laugh. You talk about my bias. LMAO. You are saying yes to all 4 questions. Too funny.
Absolutely not! The first step in proving that AGW causes anything is to prove that AGW exists to any appreciable degree. That has not been done to any scientific satisfaction. Once that is done then we can branch out to the other fields.
Yes
Is there enough evidence to conclude that AGW has caused any decrease in crop production?
Is there enough evidence to conclude that AGW has caused an increase in hurricanes or hurricane intensity?
IS there enough evidecne to conclude that AGW will in the future significantly lessen our crop production?
