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Bridging climate science, citizens, and policy

Beyond 4 Degrees – Catastrophic Double-Digit Temperature Increases by Mid-Century?


The UK Met Office hosted a conference in last month (Sep 2009) titled, “4 Degrees and Beyond” at Oxford University.  The bottom-line message is confirmation of what many climate activists have been saying for years: there is a much higher potential for much more warming than commonly thought.  The numbers are staggering in their implications, as I’ll detail below.

First, what did these climatologists do?  They ran the IPCC  high emissions scenario (i.e. business as usual (BAU)) in one of the few global climate models capable of analyzing strong carbon cycle feedbacks, a necessary test to truly reveal details of what our current emissions path could bring to the planet.  The reason this test is necessary was apparent in the results: the same warming that resulted from a BAU scenario without the feedbacks by 2099 occurred instead around 2060 in the BAU scenario with the feedbacks.  What implications does that level of warming by 2060 have for the globe by 2099?  Substantially higher temperatures, especially for some regions:

  • The Arctic could warm by up to  27.4°F [15.2 °C] for a high-emissions scenario, enhanced by melting of snow and ice causing more of the Sun’s radiation to be absorbed.
  • For Africa, the western and southern regions are expected to experience both large warming (up to 18 °F [10 °C]) and drying.
  • Some land areas could warm by 12 degrees [7C] or more.
  • Rainfall could decrease by 20% or more in some areas, although there is a spread in the magnitude of drying. All computer models indicate reductions in rainfall over western and southern Africa, Central America, the Mediterranean and parts of coastal Australia.
  • In other areas, such as India, rainfall could increase by 20% or more. Higher rainfall increases the risk of river flooding.

The Arctic has already warmed by ~5°F, and we’ve seen the results: the ice pack area and volume has decreased substantially in a very short time period. There’s no way the Arctic ice pack could survive temperatures 27°F warmer.  What about Greenland, whose glaciers are already melting twice as fast as they were predicted to just 10 short years ago?  Those glaciers would become rushing torrents of melt water if they are subjected to anything near 27°F warmer conditions until they completely disappeared.

Okay, the Arctic is pretty far away and who cares about the glaciers on Greenland anyway.  What about here in the good ol’ U.S.A., the greatest country in history?  Why should we spend an ounce of energy on a left-wing/global-control conspiracy theory anyway?  Large parts of the inland United States would warm by 15°F to 18°F, even worse than the NOAA-led 13-agency impacts report issued earlier this year found.  Those reports indicated 9-11°F average temperature increases were likely under BAU scenarios.  How many days a year would Colorado’s Front Range experience 90°F+ maximum temperatures?  90-120.  That’s three to four months of 90°F+ highs in what would become an average year.  There wouldn’t be relief at night since those temperatures are the ones most affected by climate change.

To put these numbers in context, policy makers are only now discussing effects leading up to 2°C warming.  The warming potential in a BAU situation blows by 2°C warming in a decade or two.  An important point arises here: the warming trend isn’t likely to be steady and linear, which unfortunately most of us are more comfortable with.  The change is likely to be as drastic as the changes seen at higher latitudes and altitudes.  If we do get to 4°C, the study says that the increase could threaten the water supply of over half the world’s population.  If we think geopolitical problems are complex and in bad shape now, wait until 3 billion people can’t get fresh water.

So, what has this study demonstrated?  That business-as-usual can no longer be business-as-usual.  Extreme warming is more likely to occur, be more intense, and occur faster than recently believed.  Average temperatures that were predicted to occur in 2099 in models that lacked realistic feedbacks instead are predicted to occur by the 2060s – a full four decades faster.  Thus, temperatures in this plausible worst-case scenario in 2099 could be significantly higher than they were expected to be.

Back to the U.S.: this study, and many other related studies that have come out this year, all point in one direction.  We must act now – by which I mean the U.S. Congress must pass aggressive legislation that deals with this threat.  We can avoid most of the dire consequences as soon as we move off of the BAU path.  The warming identified above is the worst-case scenario from the 2007 IPCC 4AR.  Despite the fact that actual emissions have kept pace that worst-case scenario, we still control the situation enough to reach peak emissions in the next decade, and reduce them thereafter.  Some consequences will still be felt – that’s unavoidable at this stage, thanks to Con-led inaction.  But not all consequences are yet set in stone, so to speak.

Cross-posted at SquareState.


2 thoughts on “Beyond 4 Degrees – Catastrophic Double-Digit Temperature Increases by Mid-Century?

  1. Pingback: U.S. Record High Temperatures Recorded At Twice The Rate Of Record Lows This Decade « Weatherdem’s Weblog

  2. Pingback: CO2 Acidifying Oceans Faster Than Oceans Can Adapt « Weatherdem’s Weblog

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