Saturday, September 28, 2013

Looking to the Future

The IPCC Summary from Policymakers (after all they got to approve every sentence of the thing) is occupying the blogs, with continued focus on climate sensitivity, ocean heat content, sea level rise and more. 

To Eli, an important bottom line can be found in the boxed statement on the last page

Cumulative emissions of CO2 largely determine global mean surface warming by the late 21st century and beyond. Most aspects of climate change will persist for many centuries even if emissions of CO2 are stopped. This represents a substantial multi-century climate change commitment created by past, present and future emissions of CO2.
which is expanded on below,
A large fraction of anthropogenic climate change resulting from CO2 emissions is irreversible on a multi-century to millennial time scale, except in the case of a large net removal of CO2 from the atmosphere over a sustained period. Surface temperatures will remain approximately constant at elevated levels for many centuries after a complete cessation of net anthropogenic CO2 emissions. Due to the long time scales of heat transfer from the ocean surface to depth, ocean warming will continue for centuries. Depending on the scenario, about 15 to 40% of emitted CO2 will remain in the atmosphere longer than 1,000 years.
Bunnies have to keep in mind that the most optimistic of the scenarios, RCP 2.6, the one where the world gets serious about climate change, requires huge reductions in the carbon dioxide emissions,
By 2050, annual CO2 emissions derived from Earth System Models following RCP2.6 are smaller than 1990 emissions (by 14% to 96%). By the end of the 21st century, about half of the models infer emissions slightly above zero, while the other half infer a net removal of CO2 from the atmosphere.
The Sueddeutscher Zeitung reports that this originally said that by 2050 emissions had to be halved to avoid the 2 C boundary, but that the Saudi's insisted this be changed to (by 14% to 96%).  The scientific consensus limited the damage because in a meeting of nations credibility is important and the full Inhofe only produces sniggling.

In looking at the projections of global temperatures, one has to keep in mind that there are different projections for different scenarios
Global surface temperature change for the end of the 21st century is likely to exceed 1.5°C relative to 1850 to 1900 for all RCP scenarios except RCP2.6. It is likely to exceed 2°C for RCP6.0 and RCP8.5, and more likely than not to exceed 2°C for RCP4.5. Warming will continue beyond 2100 under all RCP scenarios except RCP2.6. Warming will continue to exhibit interannual-to-decadal variability and will not be regionally uniform
and pay careful attention to that word exceed
Increase of global mean surface temperatures for 2081–2100 relative to 1986–2005 is projected to likely be in the ranges derived from the concentration driven CMIP5 model simulations, that is, 0.3°C to 1.7°C (RCP2.6), 1.1°C to 2.6°C (RCP4.5), 1.4°C to 3.1°C (RCP6.0), 2.6°C to 4.8°C (RCP8.5). The Arctic region will warm more rapidly than the global mean, and mean warming over land will be larger than over the ocean (very high confidence).
Somebunnies will attempt to use the wide range of projections, 0.3 to 4.8 to cast doubt.  Point out that the range for no action 2.6°C to 4.8°C, is much more precise, very scary, and in no way a walk in the park for their kid's kid's.

Summaries at Real Climate

6 comments:

Sou said...

That chart is the most informative and most disturbing chart of the lot IMO. It lets us choose the budget for the future.

A generous budget and we're probably trading the future of civilisation for what? No advantage that I can see.

A reasonably tight budget and many of us (say, 60% of people alive today) will reap benefits in their lifetime, not to mention give some hope that in the future it won't be as bad as it would otherwise be.

William Connolley said...

> The Sueddeutscher Zeitung reports that this originally said that by 2050 emissions had to be halved to avoid the 2 C boundary, but that the Saudi's insisted this be changed to (by 14% to 96%).

Don't understand that. Or "By 2050, annual CO2 emissions derived from Earth System Models following RCP2.6 are smaller than 1990 emissions (by 14% to 96%)". The emissions in the RCPs are from economic not ESM, surely? Is there a confusion between emission and concentration here?

Anonymous said...

Sorry to be somewhat off topic, but Roger Junior has made his latest offering on AR5. Lots of twisting and spinning of the facts, with a smoke screen thrown in for good measure.

The bunnies aren't going to let him get away with it are you?

J Bowers said...

Alexander Graham Bell turns out to be a welcome MSM BTL antidote to Dyson and Happer in this week of AR5 releases.

"Every town or city has a vast expanse of roof exposed to the sun. There is no reason why we should not use the roofs of our houses to install solar apparatus to catch and store the heat received from the sun. Solar heat [can be used].... to heat a liquid and store the liquid in an insulated tank... applying even the Thermos bottle principle of a partial vacuum around the tank.” (1914)

"Coal and oil are......strictly limited in quantity. We can take coal out of a mine but we can never put it back.” “What shall we do when we have no more coal or oil?” “[The unchecked burning of fossil fuels] would have a sort of greenhouse effect.” “The net result is the greenhouse becomes a sort of hot-house.”(1917)

Anonymous said...

"Somebunnies will attempt to use the wide range of projections, 0.3 to 4.8 to cast doubt."

Done by a mainstream newspaper in France (Liberation) - given the newspaper and the implication of on of its journalist, I bet it was not maliciously done, it was a mistake done by an inexperienced journalist.

Result was, however, unfortunately predictable.

bratisla

Anonymous said...

"The emissions in the RCPs are from economic not ESM, surely?"

Yes and no. During the scenario development for the CMIP5 they had started with assumed radiative forcing, then reverse-engineered compatible concentrations and emissions using IAMs.

But you can also use ESM (with carbon cycle stuff, interactive land vegetation etc) to diagnose emissions from concentration-driven run (the key AR5 reference is: Jones, et al 2013: Twenty-First-Century Compatible CO2 Emissions and Airborne Fraction Simulated by CMIP5 Earth System Models under Four Representative Concentration Pathways. J. Climate, 26, 4398–4413.)

There are also emission-driven RCPs with emissions derived from the IAMs, but that's another thing...