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Statistical evidence of global warming ??
Here in Washington state, this is what we have noticed over the last few years:
- Initially, nicer winters, drier, warmer, less snow
- Subsequently, very wet years
- Then lots of snow in winter
- Then more extreme weather - either very cold or very hot, but OK on average
- Also, rain changed from drizzle to heavy rain
- Is the next step going to be drier and hotter, turning to semi-desert?
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Replies to This Discussion
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Permalink Reply by DoonePlace on -
You need more data for your state but generally the coefficient of variation of climate variables increase during periods of climate change: more rainfall, more dry periods etc.
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Permalink Reply by John Logsdon on -
I suspect the climate changes in Washington state will be very much as they are in the UK.
Things will get colder in winter and eventually hotter in summer. It depends mainly on the thermohalide ocean drift which will slow down with ice melting because of a reduction in salinity. This goes north on the west side of the major continents of America, Africa, Europe and south on the east sides. Hence the usual massive snow in NY and Japan followed by sweltering heat. The drift goes south of India and Africa and is one big figure of 8. There is a deeper reverse current beneath it.
The problem is that melting waters from the Arctic will reduce salinity and the upper and lower currents could reverse. Thus instead of enjoying warming water coming up from the south during winter, you are likely to 'enjoy' more BC or Alaskan waters. At the moment, the oceans are going through a cooling cycle which will last possibly another 10 years. Thereafter there will be considerable heating of the planet so it will be some time before we can enjoy the benefits. Meanwhile further south, there are rainfall issues. The Mediterranean countries, like California, are suffering prolonged drought.
The other thing as already said is that variability will increase as the climate becomes unstable and this will continue until a new stability is found. Expect flash floods, fires and the occasional nice day! But I would rather live in the UK , Washington state, BC or similar than further south...
To comment statistically is very difficult - it is a moving average issue but there are not sufficient observations to build a time series type of model. Any model must link all parts of the globe, air/wind as well as sea at many levels and the effects of land mass. Since the time to a new stable climate is probably in the 100s of years, this is something where the science needs to be the fundamental modelling tool, not empirical observation.
Enjoy the prospect of warmer climates and also the rain. We know all about rain in Manchester!
For some useful information, see a set of slides from a talk we had here in Manchester in 2004 from Peter Challenor of the Southampton Oceanography Centre.
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Permalink Reply by Vincent Granville on -
If you would paint our entire planet in white, temperatures would go down. If you'd paint it in black, temperatures would go up. One argument that is sometimes used to justify global warming is "fewer ice fields = less white = more black = hotter". However, higher temperatures means more ocean evaporation, which in turn means more clouds, which in turn means more white and cooler temperatures: clouds reflect light as much as glaciers or ice -- they are as white as ice when you look at them from above. It would eventually result in cooler temperatures above the oceans (because of the cloud coverage), but possibly higher continental temperatures in places where glaciers disappeared.
In addition to this, there is a discussion as to whether global warming is good or bad. In the short term it's bad because it creates chaos, but in the long term, think of Chinese, Indians growing palm trees in Canada or Antarctica, and avoiding over-population with its negative side effects (wars).
The purpose of this message is to show that even the best analytical models will fail if based on incomplete data or assumptions, or ignorance of feedback loops. Getting comprehensive, good data is by far the biggest challenge that data miners and predictive modelers are facing. Without such data, models could be very wrong.
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Permalink Reply by John Logsdon on
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Vincent is right of course (well I may argue about the use of the word chaos) but the problem is timescales. If the world moves to another quasi-stationary state, this is likely to take many generations to find, during which time water, food and simple local overpopulation will lead to wars. We may already be seeing this effect although of course it is not possible to say that definitively. In the meantime we can only reduce the rate of change in the hope that, if that were to become zero, the stationarity would be achieved earlier. It is the change that is damaging.
There is the more apocolyptic view that we may be making the planet uninhabitable in the long term, in which case the key research should be in space so that the human race - or some of it anyway to be be decided in some arbitrary way - will survive. This is the view I believe of Stephen Hawking with whom I would not like to argue.
Analytical models have their uses but while people should not confuse correlation with causality, equally they should not ignore the possibility that if the probability of us causing ultimate damage <1, it is probably not 0.
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Permalink Reply by Vincent Granville on
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There's also a possibility that models are outdated, based on data that is 4 years old. The trend might have changed 2 years ago. It's very difficult for me to have a good opinion on this issue -- I live 20 miles East of Seattle, 800 feet above sea level, and for the last 2 years, we got many more snow days, more 25-degree days, and fewer 95-degree days. But it might be very local.
I used to work in environmental statistics back in 1996, but it was related to storm modeling (spatial-temporal processes) and rainfall time series, with Prof. R.L. Smith.
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Permalink Reply by John Morcomb on -
Actually the earth in a whole has been cooling for the last several years. Arctic ice has been expanding at a record rate. Based on the information received from several solar sciences and a little input from NASA we will probably see a cooler summer and more precipitation. This is based on several models used as the earth we know has gone through several cycles in the past several hundred years. To what degree will each cycle be is hard to tell, but to what degree do we play is also hard to tell considering the evidence of the past where there is very little human involvement and extreme weather patterns we still cannot explain. There are too many factors involved in the formation of weather that make this an almost impossible beast to predict.
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Permalink Reply by Matt Coates on -
I completely agree that these processes are very difficult to predict and we may not have enough data (or understanding) to be really certain about the nature of any long term trends. But expansion of Arctic ice? Is this really the case? All of the reports I have seen recently have been of a massive reduction in arctic (and antarctic) ice over recent years, with a failure to refreeze after the summer melt. Do you have any data to support this claim?
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Permalink Reply by DoonePlace on
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He is probably making his prognosis based on this image (BTW, it looks like the Arctic ice is decreasing generally and is certainly not increasing at a record rate)
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Permalink Reply by Matt Coates on
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Very interesting graph. Thanks for posting. Where did it come from?
Presumably "Sea Ice extent", measured in terms of area, is only part of the story and total quantity of ice is the more important metric. Are similar data available for mass of ice?
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Permalink Reply by John Crout on -
Regarding the effect of light reflection: What Vince wrote is true, I believe. I wonder if there is any work (theoretical or otherwise) that addresses the spectrum of radiated energy. Energy is indirectly related to wavelength. (An easy-to-read page is here: http://heasarc.gsfc.nasa.gov/docs/xte/learning_center/universe/ener....)
Reference to the effects involving the visible spectrum lean towards the production of an oscillation. I wonder where other wavelengths fit. Since absorbed energy is more-often converted to heat, the effect of visible wavelengths may be unnoticeable, simply because of them.
The link above, says that light (visible) is on the lower end of the energy spectrum.
I didn't have a chance to read everyone's reply so may have missed relevant content.
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Permalink Reply by Joseph Foutz on -
I’m chiming in on this discussion a little late, but…
First a general thought on global warming - defining it is an incredibly difficult task. An increase in global average temperature? Surface temperature, atmospheric temperature, ocean temperature… There is no global temperature and there is no global thermometer. We have a collection of temperature monitoring stations scattered throughout the globe that provide surface temperatures over a relatively short time range, and there is satellite data that goes back a very short time range. Lots of other things have been used as proxies in order to yield a larger dataset (tree-ring data, sea ice, etc.) mostly with horrible results. e.g. Initial work on tree-ring data showed a “hockey stick phenomenon” that was later shown to be a cooked result of the model. The model always generated the same result, even when purely random data was fed into it. Tree ring data continues to be used, and I understand that its application has been improving slightly, but results are still very suspect. Sea ice is related to global temperature, but not tightly related, and precise data goes back a short timespan. Difficulties with monitoring station data involve improving technology and the fact that the collection of global temperature monitoring stations is constantly changing, new ones come online and old ones go offline. Nowhere has this been more exemplified than the “hockey stick phenomenon” of the 80s and 90s that showed rapidly rising temperatures. (“Hockey stick phenomenon” is used for all sorts of different time frames and data sets in global warming literature.) The reality was that the dataset has big problems (e.g. as the Soviet Union broke up, a lot of cold-weather monitoring stations in Siberia went offline). And even if one had a relatively good dataset, climatological models are extraordinarily complex and leave almost infinite room for misspecification error. After that, I’m not even going to begin to delve into the even trickier question of how to define the question of whether global warming, if it is happening, is a natural phenomenon or a human-caused phenomenon. To contradict the former Vice President, the debate isn’t over - it’s barely begun. I don’t believe there is anyone on earth that has an even relatively good grasp of what’s going on with global temperature trends.
I have an interest in climatology if for no other reason than that I lost two-thirds of everything I owned to Hurricane Katrina. But the simple reality is that the science is in its infancy and major advances need to be made. As a society, we are flooded by reports from politicians, the news media, and scientists on global warming that greatly exaggerate the state of knowledge we have on the issue. Personally, I resent it.
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Permalink Reply by Joel Pulliam on
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Joseph, couldn't agree more.
I'm not a climatologist. I'm an engineer with a good statistics background and some common sense. I find the justification of anthropological global warming to be riddled with serious holes.
Yet, if you just apply logic and question the litany, you're considered a 'denier.'
I'm open to AGW. And I don't deny that mean surface temperature appears to have gone up in a significant way in the last few decades (although our climate has been much hotter in the not too distant past). I also understand the science behind the greenhouse effect. All of that makes sense to me.
What doesn't make sense is the politicalization of this topic and the maniacal focus on CO2 versus other important topics like clean drinking water, particulates in the air, etc. Also, the claims that global warming is bad and/or leads to a more volatile climate are even harder to prove, IMO.
To me, when people assume that AGW is settled, bad and we must take draconian measures to cap CO2, they're just showing their mathematical and economic ignorance. Sadly, that ignorance is now in abundance.
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