2011-01-17 16:02:57Climate change to continue to year 3000 in best case scenarios
John Cook



New research indicates the impact of rising CO2 levels in the Earth's atmosphere will cause unstoppable effects to the climate for at least the next 1000 years, causing researchers to estimate a collapse of the West Antarctic ice sheet by the year 3000, and an eventual rise in the global sea level of at least four metres.

The study, to be published in the Jan. 9 Advanced Online Publication of the journal Nature Geoscience, is the first full climate model simulation to make predictions out to 1000 years from now. It is based on best-case, 'zero-emissions' scenarios constructed by a team of researchers from the Canadian Centre for Climate Modelling and Analysis (an Environment Canada research lab at the University of Victoria) and the University of Calgary.

"We created 'what if' scenarios," says Dr. Shawn Marshall, Canada Research Chair in Climate Change and University of Calgary geography professor. "What if we completely stopped using fossil fuels and put no more CO2 in the atmosphere? How long would it then take to reverse current climate change trends and will things first become worse?" The research team explored zero-emissions scenarios beginning in 2010 and in 2100.

The Northern Hemisphere fares better than the south in the computer simulations, with patterns of climate change reversing within the 1000-year timeframe in places like Canada. At the same time parts of North Africa experience desertification as land dries out by up to 30 percent, and ocean warming of up to 5°C off of Antarctica is likely to trigger widespread collapse of the West Antarctic ice sheet, a region the size of the Canadian prairies.

Researchers hypothesize that one reason for the variability between the North and South is the slow movement of ocean water from the North Atlantic into the South Atlantic. "The global ocean and parts of the Southern Hemisphere have much more inertia, such that change occurs more slowly," says Marshall. "The inertia in intermediate and deep ocean currents driving into the Southern Atlantic means those oceans are only now beginning to warm as a result of CO2 emissions from the last century. The simulation showed that warming will continue rather than stop or reverse on the 1000-year time scale."

Wind currents in the Southern Hemisphere may also have an impact. Marshall says that winds in the global south tend to strengthen and stay strong without reversing. "This increases the mixing in the ocean, bringing more heat from the atmosphere down and warming the ocean."

Researchers will next begin to investigate more deeply the impact of atmosphere temperature on ocean temperature to help determine the rate at which West Antarctica could destabilize and how long it may take to fully collapse into the water.


The paper "Ongoing climate change following a complete cessation of carbon dioxide emissions" by Nathan P. Gillett, Vivek K. Arora, Kirsten Zickfeld, Shawn J. Marshall and William J. Merryfield will be available online at http://www.nature.com/ngeo/index.html


2011-01-17 16:59:05Fun stuff
Daniel Bailey
Daniel Bailey

BPL has a paper submitted for publication that takes Dai et al 2004 and 2010 and extends their results into the future via a mathematical model which examines the fraction of Earth’s land surface in severe drought (PDSI <= -3.0). That fraction was 6% in 1870, 12% in 1970, 21% in 2005. 

In each and every one of 10,000 simulation runs the fraction of Earth’s land surface in severe drought exceeds 70% by 2052 ± 2.5 years.


FYI, Tamino has examined BPL's work (said he was afraid BPL might be right).

2011-01-18 05:30:08Cruel response
Julian Brimelow

Oh dear. more cheering news.  And more counterintuitive results-- floods from higher PWV contents from higher SSTs, and at the same time increase in area affected by drought. Accelerated hydro cycle is turning out to be not much fun, and also making it really hard to explain the consequences to lay people.

Just looked at a drought monitor product on John's latest thread and that area north of Brazil where the flooding has been was in a drought until recently (just like Queensland).  I'll post about this on the thread.








2011-01-18 06:45:50

I hate unexplicated TLAs.
2011-01-18 07:03:10
Julian Brimelow

Sorry Neil, were you perhaps referring to PWV?  If so, it stands for precipitable water vapour content-- the depth of water obtained if one could condense all the water vapour in a 1 m^2 column extending through the depth of the atmosphere.





2011-01-18 08:12:10Glossary for acronyms?


While reading this and some other posts in the forum, I tend to also get confused by many of the used acronyms. A contributing factor for me might be that English is not my native language which makes it even harder to try and figure out what they might mean....

Should we perhaps have a document somewhere on SkS which can be updated by authors (or at least admin authors) collecting and explaining the used acronyms?