I know from my Heat transfer classes that the ground can radiate heat to the sky. Effectively this is the main source of heat transfer in an environment absent conduction and convection effects so there is only radiative heat transfer. If the sky is clear, the ground is effectively radiating heat to the sky which appears to have a termperature of around 4 degrees K as I recall. this means there is a large radiative heat transfer.
If there is a could cover, the sky (cloud) is at a much warmer temperature and nearly the same as the ground so the net heat transfer is very small compared to the open sky heat transfer.
This effect is not related to the GH gas properties at all. I I had to guess, I would think the cloud effect has much greater effect than the CO2 concentration changes we have seen. The only question is how much the cloud effect provides in terms of a blanket to protect the earth's surface at night.
I think it might be possible to construct some simple models of the atmosphere and examine the effects of CO2 and cloud cover in isolation. Without trying to include so many additional variables it might be possible to estimate the effects of CO2 concentration compared to a cloud effect. If these were the only variables within the simulation it might show some useful data without having to go through the full blown or more complete modeling problems.
Although I am contributing to the number of posts here, doesn't this say is all? This is really what is is all about, to create 'debate' were the evidence doesn't credit it? This is how the Apollo moon conspiracy, and UFO theorists gain publicity for their cause, it needn't be rational only controversial. Unfortunately, unlike these cases, it is not merely an academic argument. Climate change has important practical and moral consequences for humanity. Do the fake Skeptics realise this or simply don't care?
In 2002 the leading Republican consultant Frank Luntz, conceded that the party has "lost the environmental communications battle" and urged its politicians to encourage the public in the view that there is no scientific consensus on the dangers of greenhouse gases. In a memo to President George Bush, Frank Luntz wrote: "The scientific debate is closing [against us] but not yet closed. There is still a window of opportunity to challenge the science," Mr Luntz writes in the memo, obtained by the Environmental Working Group, a Washington-based campaigning organisation.
"Voters believe that there is no consensus about global warming within the scientific community. Should the public come to believe that the scientific issues are settled, their views about global warming will change accordingly.
"Therefore, you need to continue to make the lack of scientific certainty a primary issue in the debate."
The phrase "global warming" should be abandoned in favour of "climate change", Mr Luntz says, and the party should describe its policies as "conservationist" instead of "environmentalist", because "most people" think environmentalists are "extremists" who indulge in "some pretty bizarre behaviour... that turns off many voters".
Words such as "common sense" should be used, with pro-business arguments avoided wherever possible.
non-mag. I didn't mention Glaciers. They are another possible threat but not as clearly defined. Declining water tables are a real problem.
Yes there is a lot of Natural Gas at present. But there is also a rapidly growing demand as well. Supply & Demand determines prices, not just Supply.
I didn't suggest that temperature change was the cause of the explosion in jellyfish numbers. It is most likely overfishing taking out the predator wish so their are fewer around to eat baby jellywish.
The point of my post to William is that we have multiple threats to our food supply as well as the oppurtunities. To just take a simple 'we can solve every problem because we have done so in the past' mindset is a bit PollyAnna for my taste.
Particularly when many of our 'solutions' tend to only be temporary answers. Using ground water to increase crop yields is a reasonable idea. But not a permanent solution since it runs out eventually. Good for a few decades but not forever.
The Himalayan glacial melt was only 8% of what was predicted over the last several years.
There's a large natural gas surplus right now - fertilizer should be cheap.
Temperature change was only one of many possible explanations of the increased jellyfish population in the Sea of Japan.
This is the type of information that makes me realize you can't just listen to "experts" and trust what they are telling you. You'd better listen to varying points of view and do research of your own before taking one side of this issue.
Yes crop yields have shown huge improvements ove the last 1/2 century. However the rate at which yield increase is continuing is dropping off. In the 70's it was often 5%, now it is often 1%. And yields of some crops in some countries have actually started declining. Wheta and Rice in China for example.
There is room for improvement by transferring the best practices all over the world.
However there are also problems with how our agricultural systems work.In some ways the means that have delivered these increases are not sustainable for much longer, or at the very least are under threat. For example:
Ground water is a major aspect of irrigation without which we could not get anything like the current yields. But ground water resources are being depleted around the world. In Northern india water tables are now often over a kilometer down and dropping. So to in the wheat growing belt across nortern China. And in the US Mid-West the Oglallah Aquifer is in steep decline.
Modern agriculture can't function without Fertiliser. And the main feedstock used to produce fertiliser is Natural Gas. With demand rising for a range of reasons prices are rising. Natural Gas costs are now about 90% of the manufacturing cost of fertilisers. And somewhere into the future, we aren't sure where is Peak Gas, just like Peak Oil. Many in the world can't use fertilisers if they are too expensive.
It is estimated that 1/3rd of agricultural land around the world is loosing soil faster than it is being created. Rates of sediment flow down the worlds rivers are now 3 times the level they were over the geological history of then Earth. Humanity is now the most powerful source of erosion on the planet.
The use of Nitrogenous fertilisers is also generating lots of run-off that is having a detrimental impact on the oceans. And increasing the generation of Nitrous Oxide, a 2nd tier GH gas with a long atmospheric lifetime.
In the oceans, various fisheries around the world have collapsed. Some recover but others haven't. Estimates from current trends are that effectively all the worlds fisheries will have collapsed by 2050. And already some existing fishing grounds are suffering from huge expansions of jellyfish numbers - clogging nets and in a few cases in the Sea of Japan, capsizing fishing boats.
Then add in global warmings quiet ugly cousin - ocean acidification. The chemistry of what happens as CO2 is added to seawater is well understood and it has a detrimental effect on the capacity of shell forming creatures to maintain the integrity of their shells. Early signs of this are already being observed and it is estimated that a CO2 level of around 430 ppm will be the critical threshold for many species that form the basis of the marine food chain.
And the sea provides the primary source of protein for about a million people.
So scope for improvement? Yes. But also massive threats and challenges.
I don't think a test chamber to look for warming is technically viable. The reason is that to simulate the GH effect you need to be able to simulate the vertical temperature profile through the atmosphere as well to as the pressure gradient.
However, at a lower level, test chambers that can measure the detailed spectroscopic properties of the individual atmospheric gases and gas mixtures at various temperatures and pressures. This work has already been done. The HiTran specrtroscopic data base has data oon around 2.5 million different absorption lines for around 30 gases. It is this data that is the basis of the calculations of the GH impact of the gases.
It often seems that people see the theory of Global Warming as something that came out of left field in the last 20-30 years from a few people. What most people don't realise is that the basic theory goes back to the 19th century, and that starting in the 1950's the basic Radiative Heat Transfer science was put onto an extremely solid footing through research across many disciplines of Physics and Chemistry. It is a profoundly well researched field that forms the basis if many technologies such as sensor heads on heat seeking missiles, Early Warning satellites, many branches of Astronomy and even the design of Microwave ovens.
This is perhaps why so many scientists working in Climate Science are not good advocates for it. Much of the science is so well established that they are rather non-plussed by the need to defend it. That is why the debate about AGW happens in the public spehere. In academia the basics are very well accepted because they come from the most fundamental aspect of science.
That is not to say that there aren't uncertainties, there are. But they are uncertainties around how much, how fast etc. Not uncertainties about whether.
Something to consider. If AGW is so invalid as the supposed skeptics say, why are they arguing this in the public spaces? Why aren't they arguing this in the halls of Academia? A common response to this is 'they ignore us', again uttered in the public sphere. But are they being ignored? Or are they just plain wrong? Its important to remember that even in Academia their are still cranks - the Tenure system that give academics the independence they need can also give cranks a platform.
I would reassess my opinions about AGW when skeptic scientists engage in serious, well executed, science that I can see is not riddled with logical flaws, bad experimental designs, unjustified conclusions etc and that then produces significant results counter to the consensus. I have never seen that yet.
Going through the 'information' from Friends of Science:
'The Earth is Cooling'. They show a very short term trend in atmospheric temperatures. Warming of the atmosphere is only about 3% of the heat accumulated due to AGW with 90% of it going into the oceans. So short term atmospheric temperatures can be strongly impacted by what happens in the oceans. This is why trends as short as 10 years aren't considered terribly important. This is just natural variability within the atmosphere. Normal variability in any decade is typically around 0.2C and since the underlying warming trend is of a similar magnitude, the variability can swamp the trend over those short time scales. The usual time scale for measuring Climate change is 25-30 years. The FoS graph doesn't even show the preceding warming. Its intent is to mislead. Also, when we look at warming in the ocean we see a much more clear cut trend - see my earlier post of the data from Cherch et al. In fact, comparisons of the observed warming in the top 700 metres of the ocean vs the top 2000 shows that more heat is being cycled deeper down, holding the surface cooler and thus driving atmospheric temps the same way. But warming is still happening, just somewhere else at the moment.
'The Sun Causes Climate Change'. Their graph is reasonable but the conclusion they have drawn from it isn't. Changes in solar output most certainly affect climate but that isn't the only factor that does. CO2 is another. When CO2 levels are fairly constant, solar explains the past trends. But when CO2 is changing it comes into play as well - as their graph shows right at the end. During the last 1/2 century or so temps have risen while Solar has if anything declined slightly.
'Al Gore was Wrong About Carbon Dioxid'. Then they drag up the 800 year lag between temperatures and CO2 from Ice Core records. What they don't tell you is that a lag like that is what is expected. Because Ice Age cycles are driven by several factors, CO2 being one of them. Orbital changes called Milankovich Cycles trigger small warming and cooling pressures. This changes the temperature of the oceans, altering its CO2 holding capacity (Henry's Law). So CO2 moves between the ocean and atmosphere. This change in CO2 levels then contributes an additional warming or cooling. The 800 year lag (it is actually more variable than that because of other factors) is due to the fact that that is approximately how long it takes for bottom ocean waters to cycle to the top.
'Violent weather isn't getting worse'. Here they use just one index of one type of violent weather for a part of the world. I prefer a more Global measure of this. Munich Re, one of the worlds major re-insurers, the companies that insure the insurance companies, recently published the count of the number of catastrophic weather events. They ought to know, they have to pay for it. Geologic events were relatively steady over the 40 years but weather/climate related events had nearly tripled. Also FoS are playing a bit of a con here. Trying to use arguments about what has already happened as evidence about what is likely to happen in the future.
'Its been hotter'. Absolutely true. But then they suggest that because Man wasn't there then we aren't the cause of anything know. But they don't highlight CO2 levels in the past. There is a good correlation between CO2 levels and climate over the last 600 million years. Where the CO2 comes from isn't relevent. A lightning strike can start a forest fire. Or a nmatch can start one. They are arguing that because lightning starts fires a match wont!
'Climate Computer Models Are Proven Wrong' First they use Lindzen & Choi, a paper that has been heavily criticised for the methods it uses, only using samples from part of the tropics to . I could point you at other papers showing the warming occuring from a range of satellites, not just ERBE.
Then they throw up the 'missing hotspot' argument. Two problems with this. Observations using weather-balloons are known to have significant issues with measurement of air temperature at high altitude due to solar heating of the instrument package. Satellite measurements of the Upper atmosphere are also well known to include significant cool biasing of the signal they read due to much of it originating from the cooling lower stratosphere. Allow for that and the upper stratosphere has warmed. Prof Richard Lindzen (from the previous paper) has said himself that if the measurements don't show a hotspot, their must be a problem with the measurements.
Then heating of the oceans. Modelling the flow dynamics of the oceans is one of the harder areas in climate modelling and is improving over time. This is one of the factors that leads to some of the uncertainties in the models. However to then say the models are wrong is a statement intended to create the impression that they have no predictive power at all. Basic warming doesn't need climate models to predict it. It can be estimated from basic thermodynammics. The purpose of the models is to improve the predictive ability beyond that so we can get better estimates of the likely pace of warming, not its final outcome.
If we could only discover SOME way of actually intentionally CAUSING a bit of Global Warming, we could open up MILLIONS of acres of previously unfrozen, green, fertile farmland that is now too cold to farm.
Too bad the average ground, air, and oceanic temperatures are solar activity dependent, and there is literally nothing mankind can do within an order of magnitude of what would be required to warm the planet. :/
Believe what you want. I don't agree with your view as yields can go only so high and how much we actually grow is more dependent on the availability of cheap energy than farming methods or hybridization. When peak oil occurs, as it will when demand picks up, the bump in the road will be felt when fuel prices rise, thus affecting not only the farmers but the transport system that brings food to market. And that matters.
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