As for PETM, try Wikipedia for starters…

Nobody cares about the other greenhouse gases? That surprised me until I recalled that you consider the RealClimate guys nobody.
http://www.realclimate.org/index.php?p=227

David – as for the PETM, who was generating the carbon dioxide emissions that caused that? Or was it the other many greenhouse gases that nobody seems to care about?

Aaron

Briefly, carbon dioxide warms the planet as a so-called greenhouse gas. It is easy to find many separate ways to determine that, especially in the last 50 years, humans have put a huge slug of carbon dioxide in the air by burning fossil carbon. Therefore it is already warmer than natural, but it is going to get worse.

See the IPCC reports.

pough — Yes, the rate of increase appears to be without precendent in the paleoclimatological records. The last time anything approaching this rate of increase was PETM. Carl Zimmer can tell you better than I what happened to the large mammals ( > 5 kg) of that age…

Pough – Perhaps in an attempt at brevity I was too brief.

Perhaps.

Historical atmospheric carbon dioxide levels are correlated with global temperatures through ice core sampling. The temperature is derived from oxygen isotope ratios in the air bubbles in the ice. This is probably the method you are familiar with reading about.

Yes and no. You seemed to be discussing the recent past (hundreds of years) and not the distant past. From what I’ve read, ice core sampling has been used more for thousands of years of temperature data and it’s proxies like tree rings and coral growth that are used for more recent temperature reconstructions. It did a similar red flag thing that creationists dissing paleontology because carbon-dating isn’t accurate past 40,000 years does.

As for natural variation, it’s not the temperatures that are causing alarm as much as the rapidity of increase. At least, that’s the impression I’ve gotten. You seem to have understood something quite different from the available information.

David – Real Climate seems to have far too much investment in global warming to be a reliable source of information. I have no misconceptions about climatology. The planet gets warmer, the planet gets colder. I feel that this is natural variation and the historical record shows this.

The flaw in the “global warming crisis” argument is that until the last 50 years or so we had very little actual data about global surface temperatures. As more and more information is able to be gathered through actual measurements, and not through proxies, you begin to zone in on reality.

When I say that I am not convinced that global warming is manmade, that does not mean that I take every opportunity I can to club a baby panda. Do humans cause environmental damage? Absolutely. Should we limit the amounts of pollution that we produce? Absolutely. It is not a matter of global warming, it is a matter of not p**ping where you eat.

Aaron

I recommend not only Real Climate but also the side bar link to the AIP history of climatology site. Reading that ought to remove misconceptions, IMO…

extrapolations of temperatures hundreds of years ago from a CO2/Temperature ratio

Really? That’s the first I’ve ever heard of that method. Do you have any links explaining it?

The major issue I have with all “global warming” data is that it is attempting to account for very small changes in temperature by comparing real measured data, which we have today thanks to actual surface temperature readings, to extrapolations of temperatures hundreds of years ago from a CO2/Temperature ratio.

This doesn’t seem to be a scientifically sound method. You might be able to say that higher CO2 levels = higher temperatures, but to try to pinpoint such a small shift in temperature as is being discussed is certainly stretching the credibility of the relationship.

And what is the bet and how would you propose to say who won?

Hawkins has written extensively about climate change over the years, and is not a fool. There’s no reasonable possibility that he does not know about the role of aerosols. He asked the question, knowing what the answer was but hoping it would appear significant.

I’ve challenged him repeatedly to bet me over global warming, without receiving an answer.

He’s now working on the presidential campaign for Duncan Hunter.

The world has indeed survived much higher carbon dioxide levels and such.

Of course, that wasn’t a world where there were human beings trying to feed greater than 6 billion of their fellows on plants evolved and domesticated in Holocene climates…

Or a world where we needed reliable patterns of rainfall and other freshwater sources for those same people.

Of course non-anthropogenic climate change happens. But through our activities we have additionally liberated copious amounts of carbon that has been sequestered for tens to hundreds of millions of years.

Sea levels rose 400 feet since the end of the last ice age. The IPCC, in its more reasonable projections estimates sea level rises of less than 3 feet. Not much land would be lost if such a rise occurred. Valuable land can be protected, as the Dutch have done for centuries. We already know that a warmer climate opens up more land for agriculture. It happened during the MWP and it could happen again.

The idea that the MWP was a local European affair is an unsubstantiated assertion. Greenland was inhabitable and that is not part of Europe. The MWP and LIA occurred in Japan , which is also not part of Europe.

The Vostok Ice Core sample shows “a strong correlation between carbon dioxide content in the atmosphere and temperature”. Concentrations varied between 180 (ice-age) and 300(inter-glacial) ppm over the last 400,000 years. So, while you claim concentrations have risen over the last century, you haven’t separated the natural increase that always occurs during an inter-glacial period from the human contribution.

Brad Arnold,

You don’t have to imagine what would happen if CO2 concentrations doubled. All you have to do is check how high concentrations were in the Earth’s earlier history. This graph is useful in that regard. the world survived concentrations an order of magnitude higher than they are today.

If there wasn’t any CO2 in the atmosphere then photosynthesis would stop. All terrestrial plant life would die along with all the animals. i.e. we’d all be dead.

Global warming is like cancer: pain will eventually force the patient to seek an accurate diagnosis and good advice on treatment. Hopefully, the denial won’t delay the treatment until the condition is fatal.

I believe that it is unlikely that mankind will cut their emissions so fast and severely that runaway global warming will be avoided. Therefore, I recommend removing the CO2 from the air by improving nature’s ability to fix the carbon. Perhaps seeding a GMO into the ocean-it maximizes cost and scale.

Climatologists who are concerned about the effects of CO2 do not forget where the carbon in fossil fuels came from and do not necessarily argue that a warmer world is a worse world. The problem is the rate of change, which is apparently unprecedented.

human emissions of CO2 are a tiny fraction of a gas with a concentration measured in PPM.

You may consider an increase of around 50% (so far) to be a tiny fraction; I do not.

A warmer Earth is a happier, more productive Earth. The land lost to minuscule rises in sea levels is more than compensated for by land made productive in Siberia and Canada.

This is just wishful thinking. A large part of the land that could be lost to rises in sea level is currently highly productive. The land in Canada that could benefit from increased temperatures is mainly thin soil on bedrock. You are also forgetting that higher temperatures increase the water demands of crops and can also reduce yields, for example by stopping pollination of wheat and corn. They would also have a significant impact on the distribution of pests and diseases.

Now, this may also be a bit off topic, but finding the silver lining in the Cloud of Hawkins. At least he isn’t a YEC. He seems to accept The Ordovician was 440 million years ago and not 4,000. Baby steps.

The default state of the Earth over the last million years has been ice age. We are currently enjoying a respite from that default state. The little ice age was a dreadful time in human history – plagues, wars and famine devastated the population of Europe during that period. That was bad enough. Imagine the impact of a real ice age when mile-deep ice sheets covered much of North America and Europe.

The global warming alarmists imply that if we carry on burning fossil fuel, global warming will accelerate until we are all fried. They forget where the carbon in fossil fuels came from; the ancient atmosphere of the Carboniferous period when CO2 concentrations were an order of magnitude higher than today. Burning oil and coal is really just a form of recycling .

Computer models of anything other than a simple, closed system, have as much predictive value as a clairvoyant. They might help understanding of the dynamics of a complex system but they can predict nothing. If you run the models starting from a million years ago, do they predict the cycle of ice ages and inter-glacial periods? If they don’t, what use are they?

Can we actually do anything to stop global warming, if, in fact, it is partially human induced? Probably not. India and China aren’t going to stop their march forward. The best we could do is encourage them to do it cleanly. Actually, switching SE Asia from burning cow dung and plant material to electricity would be a good thing. The Asian Brown Cloud has a nasty impact on the region. It is “a 2-mile-thick blanket of pollution over South Asia, [that] may be causing the premature deaths of a half-million people in India each year, deadly flooding in some areas and drought in others, according to the biggest-ever scientific study of the phenomenon.” Be that as it may, human emissions of CO2 are a tiny fraction of a gas with a concentration measured in PPM.

Look on the bright side. A warmer Earth is a happier, more productive Earth. The land lost to minuscule rises in sea levels is more than compensated for by land made productive in Siberia and Canada. Just pray that the current inter-glacial doesn’t end anytime soon.

I appreciate the link… Though I’ll admit I was looking for more targeted information. There are a lot of different models of different quality out there and I was operating under the assumption that someone reading may have an informed starting point.

…Results 1 – 10 of about 6,050,000 for long term climate model. (0.37 seconds)…

Though the link in the article gives more information than I gave it credit for originally; an odd line break means I glanced over the more relevant, if incomplete, bits of this description:

For this purpose we used a climate model of intermediate complexity to perform a large set of equilibrium runs for (1) pre-industrial boundary conditions, (2) doubled CO2 concentrations, and (3) a complete set of glacial forcings (including dust and vegetation changes).

But of course that’s (1) subscription-only data and (2) a model specifically targeted at historical data.

Although, of course, I appreciate the snarkiness in assuming I was baiting and/or ignorant of Google.

I got that by typing ‘earth albedo’ into a common search engine. If you do some searches on climate models you should come up with a history of their development and what variables they include.

Every time I read a brief for this or that model it always strikes me that either they are not sharing the many variables they are taking into account or the models are severely simplified.

Don’t get me wrong, I understand the potential magnitude of the data involved, and the necessary shortfall of computational power, but I’d like to feel a bit more confident in current models (I personally think pollution and sustainability is an issue outside of the specter of global warming is extremely important to humanity–but I’ve not yet seen anything which gives me confidence in our ability to accurately model the climate).

I’d comment on what Sally said, but your own response pretty much covers it. The claim that global warming can only be accepted by ignoring scientific evidence is ludicrous on its face. The deniers may be able to point out one or two papers here and there, but those are completely overwhelmed by the vast majority of studies that point toward not only warming trends but human influence on those trends — four of which Carl already linked, just as a side effect of an average post. Not even as a concerted effort on his part to “prove” global warming, just during his normal blogging.

How many times do I have to say that the correct way of spelling that site’s name is Conservapaedia? (-;