Tuesday, June 19, 2007

More porkies from climate change denialists?

One suggestion (due to denialist Ross McKitrick) that is doing the rounds (Pommygranate, Tim Blair) is that carbon taxes should be tied to current degrees of global warming. This idea is flawed because climate change occurs with a lag in response to greenhouse gas emissions. NewScientist describes the lag:

‘The time lag occurs because rising air temperatures take time to make themselves felt throughout the immense thermal mass of the oceans. This "thermal inertia" means that Earth has not yet felt the full effect of today's level of greenhouse gases’.

Thermal inertia means that sea level changes will occur even if greenhouse gas emissions are drastically cut. This is quite apart from time-to-build issues involved in constructing new power generation technologies and in making investments to adapt to sea level changes and other consequences of climatic shift.

There are also cognitive lags in the brain-functioning of the denialist camp. The need for anticipatory policies has been extensively discussed in the climate change literature.

One wonders what Ross McKitrick is on about – these lagged effects have been discussed for years.


pommygranate said...


How long are thre expected lag effects?

hc said...

Pommygranate, The figures suggested in the New Scientist suggest very long lags indeed. If carbon emissions were cut drastically now temperatures would continue to rise for another century or more.

Anonymous said...

I suppose that is the famous "pipeline" that Hansen and Gore talk about.

So it is obvious that the warming of 1976-1998 was caused by something that happened in the 19th C., or at least before WW2. What could that have been?

Anonymous said...

Telling a few porkies yourself here... aside from using emotive terms like "denialists", your comments just don't make much sense.

Either there is a significant lag or there isn't. If there isn't, then the formula works fine - but if there is, then the temperature changes since the 1970's were caused by much earlier events

hc said...

Anon, The model suggests climate at time t, C(t) depends on current and past cabon emissions e(t),
e(t-1),....e(t-100) not that C(t) depends only on e(t-100). It is a 'distributed lag'.

Cutting current emissions will have a small imnpact but the cuts must be sustained to have a large effect.

pommygranate said...


I'm afraid 'anon's right.

If you are correct that the lag in temperature to changes in CO2 really is measured in centuries, then the 0.6C warming since 1970 is utterly irrelevant and cannot be put down to man.

You have just argued against your own cause.

That said, i consider myself to be one of the last of a dying species. I'm genuinely agnostic on AGW. I have an open mind. Show me some convincing data and ill join one of the two camps.

hc said...

Pommygranate, No anon is wrong for the reasons I made in the comment before yours. It is not an either-or issue. Current emissions will have an impact as will emissions with very long lags.