Science of Climate Change

[Graham Lappin]

Following a ruling of the media regulator that Channel 4's The Great Global Warming Swindle broke OfCom rules,

http://news.bbc.co.uk/1/hi/sci/tech/7517101.stm

What are the views on climate change?

There can be little doubt that climate change is occurring, but the debate surrounds the cause. Is it being caused by human activity, is it some "natural" process or a combination of the two?

Assuming it is human activity, is there anything we can do or is it too late?

Human activity or not, should we be doing more to cope with the inevitable?

What is the evidence for climate change being linked to human activity?

This whole area, I am a little ashamed to say, I know little about in terms of the scientific evidence. I have a feeling however, I am going to get educated.

[farmersboy]

Personally I think that man heas very little to do with climate change on the whole, and that the whole issue has become more of a religion than anything else.

I feel that this planet, of not the entire solar system, is just going through another of it's phases, and we happen to be around to witness this one.

As to evidence, the IPCC, for example, was set up explicitly to look for evidence that climate change is man-made...and guess what. they found it! That in itself should make one approach their reports very carefully...

[Mulder]

Personally I think that man heas very little to do with climate change on the whole, and that the whole issue has become more of a religion than anything else.

So, you don't think that our pouring greenhouse gases into the atmosphere in vast quantities has anything to do with climate change?

[farmersboy]

So, you don't think that our pouring greenhouse gases into the atmosphere in vast quantities has anything to do with climate change?

I don't think it's as bad as it's being painted.

I remember back in the seventies being warned (on Tomorrow's World I think it was) that we were heading for another Ice Age. Then everything went quiet, then it was the Ozone Layer (fair enough, we were damaging it, but now with the ban on CFC's it seems to be repairing itself), then Global Warming which has morphed into Climate Change.

What I would like to see is completely unbiased analysis by scientists without agendas, if such a thing is possible.

[Mongrel]

I don't think it's as bad as it's being painted.

See there's a difference between that and the outright denial of the people who want to keep their Hummers and Chelsea Tractors without feeling bad.

[Acleron]

What I would like to see is completely unbiased analysis by scientists without agendas, if such a thing is possible.

Well, everyone is biased and we all have agendas. A scientist tries to overcome those human frailties by using such things as scientific method, peer review, matching the data to their theories and being open minded about the science. Would you rather take the word of journalists, politicians and spokespeople for oil companies? These are the only groups I see who oppose the climate scientist's conclusions.

[Matt]

Personally I think that man heas very little to do with climate change on the whole, and that the whole issue has become more of a religion than anything else.

I feel that this planet, of not the entire solar system, is just going through another of it's phases, and we happen to be around to witness this one.

As to evidence, the IPCC, for example, was set up explicitly to look for evidence that climate change is man-made...and guess what. they found it! That in itself should make one approach their reports very carefully...

Well lets separate the facts from the speculation.

The spectrum of the Sun is known, we even measure it from outside the atmosphere to make sure.
The spectrum of the Earth warmed by the sun and re-emitting it's heat is known.
The thermal properties of CO2 are known.
Therefore we know that CO2 in today's climate acts as a greenhouse gas.

Clearly CO2 levels play a role in affecting our temperature, but how much?

Our models tell us that if it were not for this greenhouse effect our average global temperture would be roughly 20 degree celcius lower then it is today. It is only fair that these models recieve scrutiny. There are assumptions to be questioned, there may be unknowns which have not been factored in. Those who offer such scrutiny fall into two camps, constructive and destructive. There are those who would question the models in use with a view to making better models. There are those who simply wish to tear down current models.

One of the unknowns is the way to greenhosue gasses play a part in a shifting dynamic equilibrium.

Increased CO2 levels lead to higher temperatures - fact. However it's also true that increased temperatures lead to higher CO2 levels.

We do know that we've been releasing vast amounts of CO2 into the atmosphere over the past century and at the same time destroying natural carbon sinks through changing land use.

We do know that atmospheric CO2 levels have increased dramaticly over the past century reaching levels that haven't been seen since at elast the time of the first homosapiens.

We do know that there has been a warming trend in the average global temperatures over the last century.

Whislt it seems quite obvious that our impact is what has caused the raise in CO2 levels and the the raise in CO2 cannot fail to have a warming effect, it is suprisingly difficult to prove exactly how much this each effects are linked.

It may be argued that unknown effects step in to ensure that our release of CO2 into the atmosphere and destruction of natural carbon sinks have a minimal (or only temporary) effect on atmospheric levels of CO2

It may be argued that the earth is warming (1) due to increased solar output and (2) due to unknown mechanisms at play in our complex and chaotic cliamte system.

It may be argued that it is the warming of the earth that has lead to an equilibrium shift increasing CO2 levels rather than an increase in CO2 levels leading to an equilibrium shift wich leads to warming.

Of course this lead to two different models which can be used to predict climate. These models can be fed historical data and we can see how well they perform.

As it turns out, models which ignore the possibility of human contributions to CO2 levels don't do so well. Over that last 30 years they think there should have been less than half the warming that we've actually seen. Factor in the greenhosue effect and we see where the other half of the warming comes from.

Another indicator is the nature of the warming. If all the warming were due to the sun's increased output then we'd expect all layers of the atmosphere to be warmed. If the atmosphere is trapping heat at the surface then the upper layers should be cooling. We see the upper layers cooling.

The IPCC wasn't set up to look for evidence that climate change is man made. Clearly the claimatre has been changing for millions of years. Man may have an impact on that change. The question for the IPCC was twofold. How much of the current change is man made? What are the implications for the future?

In answer to the first question we have an answer qualified by a degree of certainty. The concensus view is that they're 90% certain that at least 50% of recent warming is man made.

The second question allows for much greater latitude in speculation. If you want to be be skeptical about climate change then it is that area you should focus on. By arguing up the role of the sun and unknowns you're simply denying the best efforts at analysing empirical evidence.

[Cuddles]

There can be little doubt that climate change is occurring

You might be surprised about that. Many deniers don't just question the cause and possible consequences, they also claim that there is not actually anything happening at all, or that there are regular cycles.

but the debate surrounds the cause. Is it being caused by human activity, is it some "natural" process or a combination of the two?

It's both. There always has been and always will be natural variation in the climate. The main question now is how much we can affect the climate compared to the natural changes. What seems likely is that we don't actually have that much effect by ourselves, but that even a small change can drive positive feedbacks which then cause much bigger changes. For example, water is a very potent greenhouse gas. If we increase the average temperature by a small amount, more water will evaporate, which will cause a much bigger change, and so on. However, more water vapour also means more clouds, which tend to reflect more sunlight and lower temperatures, so it's rather complicated to know what will actually happen.

Assuming it is human activity, is there anything we can do or is it too late?

Well, this is one area where no-one is really sure, and it depends a lot on what you mean by "do". Can we actually stop climate change? Probably not. We've already burned a huge amount of fossil fuels, and there's essentially no chance of stopping their use until they're all used up, so assuming that really does contribute to global warming, we're not going to stop it. If global warming is all natural with human contribution at all, things are even worse, since that would mean even with all our industry we don't affect things at all, and therefore certainly wouldn't be able to stop changes.

However, what we can do is be ready. Climate change has happened in the past on a much bigger scale, and life happily goes on without even many extinctions. It depends very much on what actually changes, but we may need to do as little as building better flood defenses and preparing for worse weather. On the other hand, we may need to move lots of people and move agriculture to more appropriate places. Either way, it's nothing we aren't capable of doing, we just need to first work out what is actually likely to happen and then have the political will to actually deal with it.

Human activity or not, should we be doing more to cope with the inevitable?

Probably. The main problem is human nature. Most people just don't want things to change, and won't radically change their behaviour without something big to force them to. Then there are the people who refuse to accept things that conflict with their ideology, and others who don't care what happens in the future and just want to make money now.

What is the evidence for climate change being linked to human activity?

One of the biggest pieces of evidence is that it's essentially impossible for us not to. CO2 absorbs certain wavelengths and not others. The wavelengths emitted by a relatively cool body, like the Earth, are absorbed while those from a hot body, like the Sun, can pass, which means that more CO2 in the atmosphere will trap more heat. This is pretty basic physics that has been known for well over a century.

Other than that, in general what we have are a lot of correlations. Atmospheric CO2 has increased since the industrial revolution, and various measures related to global temperatures have increased in more or less the same pattern. However, since climate is a very messy system with plenty of other factors, the correlations can be hard to find, or will be obvious some of the time but masked at other times, which is where the deniers jump in and decide that that means nothing is happening at all.

This whole area, I am a little ashamed to say, I know little about in terms of the scientific evidence. I have a feeling however, I am going to get educated.

If you look up the IPCC reports on Wikipedia you can find pretty good analyses of them in more understandable terms, along with links to the actual reports themselves. The IPCC is generally the best source to use since they are interested solely in the science without any political agenda.

What I would like to see is completely unbiased analysis by scientists without agendas, if such a thing is possible.

Which is exactly what the IPCC, and various other scientific institutes, do. Deniers like to pretend it's all political, and there is certainly plenty of political bollocks from both sides, but the actual science is done by scientists without agendas, it's only after they've made the reports that the politics starts up.

[wagdog]

I feel that this planet, of not the entire solar system, is just going through another of it's phases, and we happen to be around to witness this one.

All science can be explained away as one big coincidence. Solid masses just move around in completely random and totally unpredictable ways, but by amazing coincidence we happen to be around to witness when they move according to Newtons Laws of Motion.

As to evidence, the IPCC, for example, was set up explicitly to look for evidence that climate change is man-made...and guess what. they found it!

Since you acknowledge that they found evidence that climate change is man-made, why do you still think it is "more of a religion than anything else"?

That in itself should make one approach their reports very carefully...

Not sure I understand this logic. Are you suggesting that one should be sceptical toward any scientific theory that was validated using evidence found via experiments set up specifically to look for such evidence? That would include almost all of science.

[wagdog]

I remember back in the seventies being warned (on Tomorrow's World I think it was) that we were heading for another Ice Age.

This is a common misconception and that the deniers of man-made global warming like pointing out. When one checks the scientific journals of that decade, there were only a handful of papers speculating on a future iceage and very few, if any, claimed one was imminent. (I'd include URLs with the details, but I haven't made 15 posts yet. For now I'd recommend googling "myth ice age site:realclimate.org")

It just goes to show that the mainstream media did as poor a job covering scientific issues in the 1970s as they are doing today.

What I would like to see is completely unbiased analysis by scientists without agendas, if such a thing is possible.

All scientists have agendas. The agenda of a good scientist is to publish research that reveals something truthful about the physical world that is backed up with solid evidence. As far as I can see, the IPCC has done exactly that.

[wagdog]

Would you rather take the word of journalists, politicians and spokespeople for oil companies? These are the only groups I see who oppose the climate scientist's conclusions.

I may have a more reliable group classification for those in the anti-climate science camp.

Libertarians who believe in laissez-faire capitalism tend to believe global warming is a hoax. Proponents of this economic model (Austrian School and Chicago School of economics) believe that all costs can be internalised, but environmental causes tend not to fit within this framework -- the best they can do is to view regional pollution as a violation of private property rights. Climate change with all its indirect global effects wouldn't work at all, so they either deny it, or apply the Bjorn Lomborg strategy of claiming that high discount rates make any future climate-related damage seem very cheap in today's money.

Have a look at Naomi Oreskes's work ("You can argue with the facts") - she explains more about this connection between climate denialism and libertarian think tanks.

[Graham Lappin]

My natural inclination on global warming is to see some quantitative data. As Matt says "Clearly CO2 levels play a role in affecting our temperature, but how much?" I have searched but been unable to find data (modelling or otherwise) that actually matches the increase in atmospheric greenhouse gas with the increase in global temperatures. Moreover, the planet has gone through cyclical temperature change over millions of years, long before man was on the planet.

Cuddels says "... in general what we have are a lot of correlations. Atmospheric CO2 has increased since the industrial revolution, and various measures related to global temperatures have increased in more or less the same pattern. However, since climate is a very messy system with plenty of other factors, the correlations can be hard to find, or will be obvious some of the time but masked at other times"

I have not been able to find data showing that correlation, even given the messy nature of the weather system. But this is part of the point - it is so complex it is very difficult to be certain. I am not a denier but at the same time I am not entirely convinced. I just don't know.

I do think however that if global warming is man-made, then it is unlikely we will really do anything about it. Action needs to be by populations but the individuals will act on what's best for them. Overall therefore, I am more pessimistic on the outcome that I am skeptical of the cause.

[wagdog]

I have searched but been unable to find data (modelling or otherwise) that actually matches the increase in atmospheric greenhouse gas with the increase in global temperatures.

It depends on your criteria for what constitutes a match. There are many variables that affect temperature so it is unlikely you can point to a graph plotting CO2 levels and global temperature to reveal a straight line. There are also delays in the climate system. The warming we're experiencing today is caused in part due to CO2 released decades ago. The oceans play are part in this delay since they warm up slower than does land.

Moreover, the planet has gone through cyclical temperature change over millions of years, long before man was on the planet.

This is not a very good argument against anthropogenic climate change. I'm sure there were lots of murders of children in the centuries before Myra Hindley was born -- does this prove she is innocent?

Alternatively, what if there were absolutely no evidence of temperature swings in any century prior to the 20th. Does this make the climate scientists' job easier? Of course not, because they would have far less data with which to build theories on.

it is so complex it is very difficult to be certain.

This is why climate scientists do not simply look for correlations and conclude immediately when they find them (or fail to). They build models based on known physics and past observations, make predictions using these models, and then test those predictions -- just like in all other scientific disciplines. NASA scientist James Hansen did exactly that way back in 1988, and the temperature record since then has served well to validate his model. He actually ran 3 scenarios since he could not be expected to accurately predict how much CO2 humans would actually emit over the following two decades -- that would require predicting the boom bust cycles of the economy, the fall of communism which crashed Soviet CO2 output, etc. But what was clear was the very significant effect on temperature that varying the CO2 output had in his model. This was not an effect he explicitly programmed in; it emerged from the basic physics in the simulation. For details see:

Hansen, J., I. Fung, A. Lacis, D. Rind, Lebedeff, R. Ruedy, G. Russell, and P. Stone, 1988: Global climate changes as forecast by Goddard Institute for Space Studies three-dimensional model. J. Geophys. Res., 93, 9341-9364, doi:10.1029/88JD00231.

One can validate his predictions against the instrumental record at GISS Surface Temperature Analysis, or Google for "Hansen’s 1988 projections"

The question now arises is why do denialists single out climate models, but give a pass to equally complex physical models that make safety predictions concerning structural engineering of buildings, commercial planes, cars, electronics, etc.

[Graham Lappin]

Thanks for the information and I think you make some good points. However I do think that your point about cyclical changes has some faulty logic:

This is not a very good argument against anthropogenic climate change. I'm sure there were lots of murders of children in the centuries before Myra Hindley was born -- does this prove she is innocent?

I am trying to play "spot the logic fallacy" but I am pushed for time and so I will have to back to you on that. The changes in temperature over the years shows that the planet has a propensity for getting hotter or cooler in the absence of man and therefore those data have to be taken into consideration. Looking for such trends and fitting these into a model is conducted in science all the time.

Thanks for the references, I will try to have a look.

[Cuddles]

I have not been able to find data showing that correlation, even given the messy nature of the weather system. But this is part of the point - it is so complex it is very difficult to be certain. I am not a denier but at the same time I am not entirely convinced. I just don't know.

Did you try looking here and here like I recommended?

I do think however that if global warming is man-made, then it is unlikely we will really do anything about it. Action needs to be by populations but the individuals will act on what's best for them. Overall therefore, I am more pessimistic on the outcome that I am skeptical of the cause.

Sadly, this is pretty much how I see it as well.