Saturday, July 7, 2012

Because we’ve been asked – the nonsense thousand-year enhanced greenhouse effect

By the Editor of and first appeared here.

People seem to be a bit shy of asking questions via the blog comments and so tend to write direct to the editor. Unfortunately time constraints mean I’ll have to stop responding – I just can’t keep up with the mail. Heck, you don’t have to give your real name and emails are never published unless so requested so there is no reason for reticence. Ask via the blog.
Now, current interest seems to be on why we ridicule claims of man’s effect on climate lasting a thousand years.

While it is technically true that removal of every last molecule metaphorically labeled “emitted by humanity” from the atmosphere has a huge time horizon this is of absolutely no significance beyond activist cant.

The only points of real interest are how quickly the planet is eliminating “extra” carbon dioxide from the atmosphere – and the quick answer according to the Carbon Dioxide Information Analysis Center is 60% of everything we release annually is absorbed by the planet’s sinks (ocean, biosphere), leaving a 40% annual accrual.

And how long would it take for that rate of drawdown to return to a nil-effect level if we stopped emitting now.

You can choose any particular level you like but 350 ppmv seems popular and certainly no one claimed to have observed any effect at that level in 1987.

Assuming our hungry biosphere and absorbent seas would slow consumption at a similar rate as it increased over the last few decades and yes, the more we produce, the more the planet absorbs at about a constant all natural plus 60% of anthropogenic emission, then the quick answer is we would return below 350ppmv in less than 25 years.

I simply calculated the absorbed “human component” from the 40% residual that is assumed to be the full cause of annual year on year increase, smoothed it by using the average of current and preceding 4 years (to account for ENSO fluctuations) and decremented the current level in reverse order from 2013 – in my spreadsheet that yields 349 ppmv in 2036, the 23rd decremental step.

For those who claim the world would still be suffering warming at that point we ask “How?”
Before advocates started “adjusting” global temperature time series none of us thought the world was warming back in ’88, although we were becoming confident it had stopped cooling.
We don’t actually have large amounts of warming “in the pipeline” as activists and assorted lunatics claim, something you can see unless you think the current seasons are planetary memory from hundreds or thousands of years ago – in which case how would you have had enhanced greenhouse warming already?

Each and every year the planet warms and cools almost 4°C, peaking in July at near 16°C and cooling to 12°C in January, according to NCDC.

Unless that is response from years gone by then the planet actually responds to changes in forcing in half a year.

Why couldn’t it be from prior years? Well, for a start we actually observe it changing in response to El Niño Southern Oscillation events. Here’s a time series graphic of all the major temperature datasets tracking the ’97/’98 El Niño warming and subsequent cooling. Here’s one depicting hemispheric air temperature change through the seasons.

Earth’s warmth just isn’t that persistent and it equilibrates rapidly to changes in forcing. There’s no long latency, no year’s-long lag and no “heat in the pipeline”. What you see is what you get – all of it, done and dusted.

If humans stopped adding to atmospheric carbon dioxide levels then the effect (however slight it may be) would no longer be detectable a quarter century later – forget about a thooouuusand years. That’s just nonsense.

The real question of merit is “what is the climate sensitivity parameter really?” It’s one we are still working on but it appears to be really trivial and not worth all the enhanced greenhouse fuss.

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