Tech | December 18, 2011 | 13 comments

Hansen and Caldiera on climate sensitivity: Paleoclimate record points toward rapid climate changes

source: http://thinkprogress.org/romm/2011/12/14/386806/hansen-and-caldeira-on-sensitivity-paleoclim...

JanforGore
"Accelerating melting on the world’s ice sheets and other new observations have scientists concluding that even a two-degree Celsius rise in temperatures – a benchmark long seen as safe in global climate talks and other emissions reductions scenarios – could lead to an 80-foot rise in sea levels.

“The dangerous level of global warming is less than what we thought a few years ago,” said James Hansen, director of NASA Goddard Institute for Space Studies. “It was natural to think that a few degrees wasn’t so bad…. (But) a target of two degrees is actually a prescription for long-term disaster.”

Antarctica and Greenland are losing ice at a surprising clip, Hansen said, and methane hydrates – a potent source of greenhouse gas frozen beneath the seas – are starting to bubble up.

The key question for climatologists: How sensitive is the climate to increasing amounts of fossil fuel emissions. Last year humanity pumped almost 10 billion tons of carbon dioxide into the atmosphere, a half-billion tons more than 2009 and the largest jump in any year since the Industrial Revolution, according to the Global Carbon Project.

See also Biggest Jump Ever in Global Warming Pollution in 2010, Chinese CO2 Emissions Now Exceed U.S.’s By 50%.

The problem, those researchers said, is the “hang time” for carbon dioxide in the atmosphere. Even if greenhouse gas emissions stopped tomorrow, “climatically important” amounts of carbon dioxide and other compounds emitted today would continue to influence the atmosphere for thousands of years, Caldeira said.

See also Fossil CO2 impacts will outlast Stonehenge and nuclear waste

That kind of pressure, or “forcing,” on the atmosphere could be devastating, he cautioned.

About 55 million years ago a tremendous amount of methane was released into the atmosphere over a period of about 1 million years, and the planet heated by five degrees to eight degrees Celsius, or 10 degrees to 14 degrees Fahrenheit. The result was an ice-free planet with sea levels 230 feet higher than they are today.

In the eons since, carbon dioxide levels dropped and the ice reformed. But humanity’s emissions have the potential to send the globe back to those conditions, Caldeira and Hansen said.

“If you doubled CO2, which practically all governments assume we’re going to do, that would eventually get us to the ice-free state,” Hansen said.

Scientists don’t expect that ice to melt quickly. Assuming the current accelerated melting continues on the world’s ice sheets and glaciers, various climate models predict the ocean would rise between 1.5 feet and 2.3 feet by century’s end, said Tad Pfeffer, a glaciologist with the University of Colorado.

But the ice melted with atmospheric carbon dioxide levels at about 1,000 parts per million, Caldeira said. And he suspects that even 750 ppm, or about double today’s levels, could send the globe spiraling toward an ice-free state. Current emissions trends suggest the globe could reach that by the end of the century.

“We can’t double CO2,” Hansen added. “We would be sending our climate back to a state we haven’t adjusted to as a species.”

The time to act was a while ago, but now is much, much better than later."

Related Posts:

•A detailed look at climate sensitivity
•Climate Experts Warn Thawing Permafrost Could Cause 2.5 Times the Warming of Deforestation
More at the link
Around 28:00 minutes into the video is information on CO2.
  1. groups:
    News and Politics,   Tech,   Green,   Culture,   9 more
  2. tags:
    Health,  Climate Change,  CO2,  Deforestation,  16 more
  3. recommended by:
    Vierotchka
  4.     
    |

13 comments // Hansen and Caldiera on climate sensitivity: Paleoclimate record points toward rapid climate changes // Video

  • JanforGore
  • JanforGore
    • +3
      JanforGore  

    • Just to also relay: The floods in Pakistan, the wildfires in Russia and the drought in Somalia have all been corrolated in studies to the effects of climate change. This has resulted in millions of hectares of crops ruined effecting global economy and life and also contributed to climate migration. That surely tells us that climate sensitivity may not be as low as some studies have shown (based on balance between forcings and feedbacks) and even a 2 degree increase in temperature will lead us to more rapid changes. The science is in and we now need to seriously move on from debate to action. The people in Durban crying not to KILL AFRICA know full well the reality of what we are already facing.

    • 5 months ago
  • JanforGore
    • +3
      JanforGore  
    • Image

    • http://current.com/community/93576631_huber-and-knutti-quantify-man-made-global-...

      Good post and study (thanks to Wake Up People for posting it) to quantify man-made global warming. People who state they don't know enough and then site Conservative newspapers with a political agenda (usually using Al Gore as their whipping boy) and not scientific studies are not interested in debate, but planting seeds of doubt. The science on human forcings on our climate is no longer debatable per scientific consensus among every major scientific organization in every country globally. What is debatable however, is if we will now survive it given the amount of time we have given to deniers, media and politicians in order to cloud this crisis with their own personal agendas.

    • 5 months ago
  • JanforGore
    • +6
      JanforGore  

    • Again, this post was at nine just two seconds ago and now it drops off? I could bet there are members here who either have an in with staff members or are staff members in secret, or are just downing it over and over again or getting their friends to do it out of spite. What else could it be? There is no way certain posts should move so fast when others lay on the front page for almost two to three days. It makes no sense and this isn't the first time. I suppose those of us now being targeted for being honest will have to take it to a higher authority because this site has been co opted by cliques and bullies.

    • 5 months ago
  • JanforGore
    • +5
      JanforGore  
    • Image

    • http://thinkprogress.org/romm/2011/12/17/391462/our-extreme-weather-arctic-chang...

      The corrolation between Arctic ice loss and extreme weather is also being studied.
      ~~~
      "“The question is not whether sea ice loss is affecting the large-scale atmospheric circulation…. It’s how can it not?” That was the take-home message from Dr. Jennifer Francis of Rutgers University, in her talk “Does Arctic Amplification Fuel Extreme Weather in Mid-Latitudes?”, presented at last week’s American Geophysical Union meeting in San Francisco.

      Dr. Francis presented new research in review for publication, which shows that Arctic sea ice loss may significantly affect the upper-level atmospheric circulation, slowing its winds and increasing its tendency to make contorted high-amplitude loops. High-amplitude loops in the upper level wind pattern (and associated jet stream) increases the probability of persistent weather patterns in the Northern Hemisphere, potentially leading to extreme weather due to longer-duration cold spells, snow events, heat waves, flooding events, and drought conditions."

    • 5 months ago
  • JanforGore
  • JanforGore
    • +6
      JanforGore  

    • This is definitely worth watching.

      Deniers are in many places in many guises. You can tell who they are as well after a while. Some also have no idea about how Earth's processes even work. Therefore, it is good to have real information from a reputable scientist to back you up rather than people who only base their "beliefs" on partisan politics (especially Conservative sites that tend to mislead) or ideology, not on peer review and reality.

    • 5 months ago
  • JanforGore
    • +5
      JanforGore  
    • Image

    • http://www.skepticalscience.com/glacier-update-0809.html

      In 2009 some news outlets reported that Bolivia’s 18,000 year old Chacaltaya glacier ‘bit the dust’ 6 years ahead of projections.That finding has now been confirmed by the World Glacier Monitoring Service (WGMS) in its recently released Glacier Mass Balance Bulletin 08/09.

      In some places warming leads to more snowfall because warmer air holds more moisture, but as a rule glaciers should shrink as the climate warms. Whilst Chacaltaya might make a spectacular poster child for global warming, one glacier is not a strong piece of evidence for or against global warming. We must look at global patterns, and this is what the WGMS does.

      Because of the volume of data and the time needed to analyze it, the just released bulletin covers the 2008-2009 time period.

      The Glacier Mass Balance Bulletin reports on the state of glaciers regularly visited and measured by scientists. Satellites and aircraft measure thousands of glaciers worldwide but to make sure we can trust these measurements, and to get more detail, there’s no substitute for boots on the ground.

      Measurements of 136 glaciers from Antarctica to Canada and from Bolivia to Japan feature in this edition, although N America and Europe are best represented. Almost 90% are shrinking.

      A group of 37 reference glaciers which have been measured continuously for decades were used to provide some statistics. On average, glaciers lost around 60 cm (~ 2 feet) of thickness in each of 2008 and 2009, close to the average for this decade but faster than the '90s, and much faster than the '80s.
      _____
      There are many factors that make climate sensitivity to doubling Co2 fuzzy to estimate in regards to short term and longterm feedbacks, land changes, sea surface temperatures, glacier melt, etc. offset by positive changes such as reforestation, Co 2 decreases, etc that produce negative feedbacks and their equilibrium. Three degrees has been the consensus. I say based on the feedbacks we are already seeing now, we have to start decreasing Co2 levels now in order to avoid greater than 3 degrees this century and rapid changes to climate due to the "hang time " for carbon dioxide in our atmosphere.

    • 5 months ago
  • JanforGore
  • JanforGore
    • +6
      JanforGore  

    • These videos give sourced facts and great information about climate change and those looking to plant seeds of doubt. They love picking cherries.

      The rate of melting we are now seeing is not due to only natural factors.

    • 5 months ago
  • thedirtman
  • JanforGore
  • JanforGore
    • +5
      JanforGore  

    • In the end it will be man's behavior as well that decides where the future climate goes. Burning all the fossil fuels under the ground/in the oceans and deforesting the planet for greed are simply not options for either keeping the Earth at a sustainable climate for human health/ existence, or a healthy environment.

    • 5 months ago
more from Tech:
from the community

top videos