Global Emissions Targets Will Lead to 4C Temperature Rise, Say Studies
Studies predict major extinctions and collapse of Greenland ice sheet with temperatures rising well above UN targets
The world is heading for an average temperature rise of nearly 4C
(7F), according to analysis of national pledges from around the globe.
Such a rise would bring a high risk of major extinctions, threats to food supplies and the near-total collapse of
the huge Greenland ice sheet.
More than 100 heads of state agreed in Copenhagen last
December to limit the rise in global temperatures to 1.5C-2C (2.7-3.6F)
above the long-term average before the industrial revolution, which
kickstarted a massive global increase in the greenhouse gases blamed for
warming the planet and triggering climate change.
months on, a major international effort to monitor the emissions
reductions targets of more than 60 countries, including all the major
economies, the Climate Interactive Scoreboard, calculates that the world
is on course for a rise of nearly double the stated goal by 2100.
study by Climate Analytics, at the Potsdam Institute in Germany,
suggests there is "virtually no chance" world governments will keep the
temperature rise to below 2C, and the rise is likely to be 3.5C (6.3F)
by the end of the century.
In both analyses the current
commitments suggest a much better outcome than the estimated
business-as-usual temperature rise of 4.8C (8.6F), but are well above
the 2C maximum the UN hoped would be agreed at the next major meeting
this December in Cancún, Mexico - and even further from the 1.5C target
many developing nations argue is needed to stop the worst impacts of
climate change in their countries.
In its last assessment of the problem in 2007, the
Intergovernmental Panel on Climate Change (IPCC) forecasts that a
rise of more than 2C would lead to potential increases in food
production, but an increasingly high risk of extinction for 20-30% of
species, more severe droughts and floods, and a unstoppable "widespread
to near total" loss of the Greenland ice sheet over very long time
periods. However, at 4C it predicted global food production was "very
likely" to decrease, "major extinctions around the globe", and
near-total loss of Greenland's ice, precipitating 2-7m of sea-level rise
in the long term. As temperatures rose, the severity of floods,
erosion, water pollution, heatwaves, droughts and health problems such
as malnutrition and diarrhoea diseases would also increase, said the
"We're looking at a level which is much more extreme and
profoundly dangerous," said Ruth Davis, chief policy adviser for
Greenpeace. "It's arguable the UN process has become dangerously cut
adrift from the science of climate change."
The Department of
Energy and Climate Change said that, based on national offers of
emissions reductions made in Copenhagen, the United Nations Environment
Programme (Unep) and other bodies had calculated that it was possible to
meet the 2C target, although this would depend on the targets set
"There's more work to do if we're going to avoid a 2C
temperature rise which is why we're pushing the EU to cut its emissions
by 30%," said a DECC spokesman. "Keeping below 2C is still possible
from the high end Copenhagen accord offers, but will require steeper
action after 2020."
However, many experts said the much higher
temperature-rise estimates were a cause for serious concern that
emissions cuts proposed for Cancún were too low and not enough was being
done to prepare for further cuts beyond 2020, even though there are
still nearly six months of negotiations before the talks.
made progress but we're clearly not headed where we need to be," said
Andrew Jones, co-director of Climate Interactive, which is backed by
several universities including MIT. "No one is talking about changing
any of the 2020 proposals, so we should be worried." Climate
Interactive's model is also backed by a panel of experts including Prof
Bob Watson, chief scientific advisor to the UK's Department for
Environment, Food and Rural Affairs (Defra), and a former head of the
The Climate Interactive Scoreboard, for which researchers
check daily for updates in emissions or other targets which would reduce
pollution such as reductions in energy intensity or increases in
renewable energy, makes a medium-range prediction of a 3.9C increase in
temperatures, with a range of 2.3-6.2C (4.2-11.1F), based on committed
targets, and a more encouraging 2.9C (5.2F) average, with a range of
1.7-4.6C (3.1-8.5F) based on "potential" commitments suggested but not
enacted by many nations.
One of the major barriers to setting
higher emissions cuts was a great many countries, including Canada and
the EU, have said they do not want to increase their targets until the
US sets significant reductions, which is proving hard for President
Obama to achieve, said Davis.
Climate Analytics and Ecofys, under
the banner of Climate Action Tracker, estimate a range of 2.8-4.3C.
principal differences between the two calculations are that they use
different models, and made different assumptions about what countries
will do after their current targets expire, said Jones.
cases, there has been no improvement to the forecast outcome since the experts assessed the prospects immediately after the
The predictions will be particularly
worrying for many watchers because the 2C target was based on research
which suggested that at that level there was only a low to medium risk
of key changes to the conditions in which humans survive; however an
update of the "burning embers diagram" by the authors, published last
year by the Proceedings of the National Academy of Sciences in the US,
suggested that at 2C there greater risk in all categories, including a
significant to high risk to unique and threatened ecosystems, of extreme
weather events and a global distribution of the worst threats.
Climate Interactive Scoreboard