StraightShooters: Reasons not to panic

The phrase "catastrophic climate change" is bandied about quite freely these days and some are even losing sleep about it, including children.

But what is the evidentiary foundation of these claims?

How do we know that any temperature rise caused by a doubling of preindustrial levels of CO2 will be "catastrophic"?

Or put another way, what is the "climate sensitivity" to said doubling of CO2 in the atmosphere?

Nobody doubts that CO2 is a greenhouse gas and has a warming effect on the Earth, so additional CO2 must mean some extra warming.

But by how much, (that is, what is its climate sensitivity), is an unresolved question.

Not that the basic physics is difficult or not understood. If the Earth's atmosphere was as simple as a vial of gases in a laboratory the answer is around 1 degree C. That is to say, a doubling of the amount of CO2 in the atmosphere should, all other things being equal, increase the global average temperature by about 1 degree C.

That's all.

So where do we get all these dire predictions of impending doom, citing temperature increases of 4 or 5 degrees or more, or even of "runaway warming" frying the planet, from?

Where do they get much higher numbers for the climate sensitivity of CO2?

In a word, feedback.

What this means is that the Earth isn't a simple glass vial in a lab, but rather an enormously complex and chaotic system that is in a constant state of flux and that changes to one element of the mix affect others and that these effects can either work against another change or make it stronger.

So if any warming effect of CO2 is made stronger by one or more of these other components of the system, this is known as positive feedback.

If they work against the warming effect (in a manner of speaking - push back against it), this is know as negative feedback.

Thus the warnings of catastrophic climate change are based on the assumption (and it is only an assumption, because we only partly understand what the feedbacks are and how they work) that the climate feedbacks are positive and that this multiplies the base sensitivity of CO2 several times.

But as the short video below explains, it is very unusual for stable systems to be built on positive feedback regimes.

But the IPCC and other alarmists have assumed positive feedback in their calculations of likely future temperatures.

So what do real world observations have to say about the projections of the IPCC based upon their assumptions of substantial positive feedbacks and figures for climate sensitivity of anywhere up to 6 degrees C or more?

Well, watch the video and find out. But I can say that they haven't been doing very well and they've had to try and find something else to explain why the planet isn't warming as fast or as much as they think it should be.