What does past climate change tell us about global warming?

I left the following comment at


These guys actually are answering. This is a first actually and I am impressed that they are prepared to argue their point.

Note how the quote the National Acadamy of Sciences saying ” This is the case for the conclusions that the Earth system is warming and that much of this warming is very likely due to human activities” and in the next breath claim that the NAS are saying AGW is a FACT!

Frankly I have seen more honest explanations in Scientology books.

“What does past climate change tell us about global warming?”

In case you dont know it, your explanation uses the AGW theory to explain the question when the question is really asking for some proof of the AGW theory.




 The comment was published in the modified form shown below.

 “What does past climate change tell us about global warming?”In case you dont know it, your explanation uses the AGW theory to explain the question when the question is really asking for some proof of the AGW theory.
doug_bostrom at 13:53 PM on 8 April, 2010

Rogerthesurf, you’d do better to explain yourself. Failing that, presumably you won’t care if your post is deleted?

72.doug_bostrom at 13:53 PM on 8 April, 2010
Rogerthesurf, you’d do better to explain yourself. Failing that, presumably you won’t care if your post is deleted? “

Sorry your reply did not show up on my “My Comments” page.

Thank you for editing my comment (not)

However my point is simple.

Correct me if I am wrong, but at no point does your explanation discuss the validity of the “Anthropogenic CO2 causes Global Warming” hypothesis. 

Instead your host of explanations which are all based on the assumption that it (the above hypothesis) is fact, which actually it is not fact but as yet simply an unproven hypothesis.

Therefore all your explanations are no better than this unproven hypothesis.

I trust that is clear.



I also always post my comments and replies on my other site https://globalwarmingsupporter.wordpress.com where my readers can evaluate my questions and your answers. Check under your url and post title.


  • doug_bostrom at 07:47 AM on 21 May, 2010

    Roger, I’m not spotting the tautology. Which part of the physics do you disagree with?

  • Roger, what exactly in the theory of climate that underlies the above that you are objecting to? That, when you add more heat to our climate, global temperatures rise? That CO2 is a greenhouse gas? That greenhouse effect is real? These questions of climate physics are better addressed on other threads. For past climate, it is better to realise that it is primarily where models can be tested and constrained.
    Phil (also from NZ)

Phil and Doug,

Thanks for your answers, please consider the opening statement to the answer of the question on this page.

“If there’s one thing that all sides of the climate debate can agree on, it’s that climate has changed naturally in the past. Long before industrial times, the planet underwent many warming and cooling periods. This has led some to conclude that if global temperatures changed naturally in the past, long before SUVs and plasma TVs, nature must be the cause of current global warming. <b>This conclusion is the opposite of peer-reviewed science has found.

Our climate is governed by the following principle: when you add more heat to our climate, global temperatures rise.”</b>

The above opening statement in the “explanation” as to why there were previous warmings (when there was no anthropogenic CO2) neatly sidesteps the question.

The question, which is a very good one, is – “If there are previous warmings, why do we blame this one on CO2?”

The answer is “Because an increase in CO2 which is a greenhouse gas, is the cause THIS TIME”.

So I am saying, where is the empirical proof of this cause.

All that is in the explanation is a lot of theory which is not based on anything empirical, in fact like I have mentioned above, the explanations assume that the “Anthropogenic CO2 causes Global warming” hypothesis is fact when in actual fact there is no emperical support whatsoever. In fact previous warmings disprove the hypothesis.

Hope you can understand my point.

This comment and your answers are posted on http://www.globalwarmingsupporter.wordpress.com for the benefit of my readers.




Response: “where is the empirical proof of this cause?”

There are multiple lines of empirical evidence that CO2 is causing warming. We have a number of different satellites from NASA and Japan finding less infrared radiation escaping to space at CO2 wavelengths (Harries 2001, Griggs 2004, Chen 2007). Surface measurements from thousands of ground based stations are also finding more infrared radiation returning back to the Earth’s surface (Wang 2009). A close examination of the infrared spectrum returning back to Earth finds more infrared radiation at CO2 wavelengths (Evans 2006).

So we have independent measurements finding the same answer – which is consistent with lab measurements and simulations of an increased greenhouse effect caused by rising CO2.

If you could post this answer on your blog, would be much appreciated 🙂


Your reply is faithfully included in my blog.

I am not disputing any of the findings that you mention in your answer, although some might, but none of this information proves in any way that anthropogenic CO2 is the root cause.

My argument which is simply based on the standard scientific proof of a hypothesis, is not hard to understand, but for your benefit I will explain more.

Even in the absence of previous warmings, the earth could be heating up for some other reason. The fact that there are well documented and general agreement that there have been previous warmings, such as the Holocene Maximum, the Minoan Warming, the Roman warming and the Medieval Warm Period, which are recorded in history as well as scientific proxies and the like, make CO2 as the root cause of global warming even less likely.

The situation can be likened to the problem that pharmaceutical researchers have. If a patient is ill and you give him some of your new drug, and the patient gets well:- Did he get well because of the drug, or did he get well anyway?
Very hard to tell, so as you should be aware, this problem is solved by doing double blind tests on a large sample of patients and doing a statistical analysis of the results. (Double blind because if the patient knows if he is receiving the drug or placebo, it effects his response, as the response is also effected if the person administering knows whether it is the drug or a placebo)

To further illustrate the difficulty of proving a hypothesis, I recommend watching the following video. http://www.youtube.com/watch?v=TxiBHNeTG7o&feature=related
The video has nothing to do with CO2 or global warming, but illustrates well the problems of hypothesis proof.  A number of people died when the captain of this aircraft formed a hypothesis of what was wrong with the plane, an incident seemed to support his hypothesis, but in spite of definitive disproof of his hypothesis being readily available, because the hypothesis was incorrect, the aircraft crashed.

In fact there are a number of known things which could cause the current warming, and probably a greater number of factors which are unknown.

I hope this clarifies things for you and your readers. Please take the time to watch the video.

This response is also posted on http://www.globalwarmingsupporter.wordpress.com



 Response: “The fact that there are well documented and general agreement that there have been previous warmings… make CO2 as the root cause of global warming even less likely”

The degree and global extent of warming is still debated for certain periods (re the Medieval Warm Period) but putting that aside, we can all agree that there have been many periods in Earth’s history when the planet has experienced dramatic changes in temperature.

Why has climate changed in the past? The primary driver of Earth’s climate is and has always been changes in the planet’s energy imbalance. If anything causes a change in the energy coming in or going out, that will lead to warming or cooling. This can include the sun getting hotter, more aerosols in the air reflecting incoming sunlight, more CO2 absorbing infrared radiation, etc. CO2 is not the only driver of climate – in the past, various factors have driven Earth’s climate. The one constant is that an energy imbalance has driven temperature change.

So what does past climate change tell us? It tells us that when the planet suffers an energy imbalance, global temperature changes. It doesn’t mean CO2 is always the main driver of past climate change. The ice age cycles of the past million years were driven initially by orbital cycles, not CO2 (but CO2 does play a positive feedback role).

A crucial piece of information we learn from past history is how much climate responds to an energy imbalance. How sensitive is our climate? And what we find is when our planet accumulates heat, there is a net positive feedback response from our climate which amplifies the initial warming. Past climate change reveals a key truth: our climate is sensitive. If you impose an energy imbalance on our planet, positive feedbacks will amplify the initial warming.

What does this have to do with CO2? We know rising CO2 is causing an energy imbalance because of direct observations (satellites observing less infrared radiation escaping to space and surface measurements of more downward infrared radiation).

So we have two pieces of information from empirical data:

1. Direct measurements today find CO2 is imposing an energy imbalance
2. Past climate change finds the climate is sensitive to an energy imbalance

Our understanding of climate comes from considering the full body of evidence. You need to consider past climate change in the context of the current energy imbalance imposed by CO2.

doug_bostrom at 11:12 AM on 23 May, 2010

Roger, you should add this to your blog because it speaks to the weight of your opinion on this subject:

Some scientific conclusions or theories have been so thoroughly examined and tested, and supported by so many independent observations and results, that their likelihood of subsequently being found to be wrong is vanishingly small. Such conclusions and theories are then regarded as settled facts. This is the case for the conclusions that the Earth system is warming and that much of this warming is very likely due to human activities.

That’s from the National Academy of Sciences. You can find the press release for this just-released report as well as links to the report itself here.

What is this “National Academy of Sciences”? You can learn about it here. It’s sort of like the UK’s Royal Society but with the brand of USA on it.

The basic point is, anthropogenic warming is considered to be fact, uncontroversially so in terms of scientific understanding. If you dig into the science you’ll find past changes of climate playing the role of evidence in support of this fact.


Have done,

However I expect you to use your brain to discuss my point. I dont give two hoots what the NAS says, unless they can show me how the “Anthropogenic CO2 causes Global Warming” hypothesis is proven. Now that would be not unreasonable to expect from a bunch of scientists right?

And it might be news to you but “anthropogenic warming” is not considered to be fact, even in IPCC reports and there is an increasing body of opinion that support what I am questioning.

But most importantly, lets not forget this conversation is about whether this blog addresses the question “What does past climate change tell us about global warming?” and I am maintaining that it skirts around the real issue which is what I am raising here.



Roger, what’s to discuss? The National Academy of Sciences says anthropogenic warming is a fact, you say it’s not and you’re quite unprepared to accept otherwise. I’m a bystander to your argument with the NAS but I have to say, I attach more weight to their conclusion and not yours. Are you surprised, that I’d have to give more credit to the NAS and their conclusion based on a veritable mountain of evidence, as opposed to your personal opinion supported by a Youtube video?

What an extraordinary conversation. I’ve participated in many such yet they still leave my head spinning. Either one must leave the merry-go-round filled with folks who show every sign of technical psychosis or one must jump on and join the endless revolution of repetitions.


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