Science Daily
Date: September 2, 2007

Source: Centre for International Climate and Environmental Research

Keywords:
Global Warming, Climate, Environmental Issues, Environmental Policy,
Environmental Science, Ecosystems

Faster Climate Change Means Bigger Problems

Science Daily – The debate about what constitutes “dangerous
anthropogenic interference with the climate” has almost exclusively
focused on how much the temperature can be allowed to increase. But we
have perhaps just as much reason to be concerned about how quickly
these changes take place.

The UN Framework Convention on Climate Change (UNFCCC) aims to avoid
what is called “dangerous anthropogenic interference with the climate
system.”

However, there is no guarantee that the level of climate change – how
much the temperature increases in the future – is the only thing we
should be worried about. How quickly the changes take place can also
mean a lot for how serious the consequences will be. This was already
acknowledged when the UNFCCC was signed in 1992. It says that we must
stabilize the concentrations of greenhouse gases in the atmosphere
within a time period that allows ecosystems to adapt and economic
development to continue, and that ensures that food production will
not be threatened. This focus on rate of change has, however, not been
reflected to any noticeable degree among either scientists or
politicians.

There are a few studies that focus on the consequences of the rate of
climate change. Most of these are ecological studies. They leave no
doubt that the expected rate of change during this century will exceed
the ability of many animals and plants to migrate or adapt. Leemans
and Eickhout (2004) found that adaptive capacity decreases rapidly
with an increasing rate of climate change. Their study finds that five
percent of all ecosystems cannot adapt more quickly than 0.1 °C per
decade over time.

Forests will be among the ecosystems to experience problems first
because their ability to migrate to stay within the climate zone they
are adapted to is limited. If the rate is 0.3 °C per decade, 15
percent of ecosystems will not be able to adapt. If the rate should
exceed 0.4 °C per decade, all ecosystems will be quickly destroyed,
opportunistic species will dominate, and the breakdown of biological
material will lead to even greater emissions of CO2. This will in turn
increase the rate of warming.

According to the Intergovernmental Panel on Climate Change (IPCC), the
global average temperature today is increasing by 0.2 °C per decade.

There is also a risk that rapid climate change will increase the
likelihood of large and irreversible changes, such as a weakening of
the Gulf Stream and melting of the Greenland ice sheets. Rapid change
also increases the risk of triggering positive feedback mechanisms
that will increase the rate and level of temperature change still
more.

We know far less about the consequences of rate of temperature
increase than we do about the level. Nevertheless, we know enough to
say that if we are to avoid dangerous climate change, then we should
also be concerned about how quickly it occurs. This can have important
implications for which climate measures we should implement. If we set
a long-term climate goal – such as 2 °C – there will be many different
emissions paths we could take to reach this goal. But these emissions
paths can differ to a relatively large degree with respect to how
quickly the changes will take place – especially over the next few
decades.

Focusing on the rate of climate change can imply that we should
concentrate more on the short-lived greenhouse gases – such as methane
and tropospheric ozone – and particles with a warming effect, such as
soot (black carbon). It can also imply a greater focus on the
medium-term (the next few decades), since the fastest changes could
occur around that time.

Reference: Leemans og Eickhout, 2004, Another reason for concern:
regional and global impacts on ecosystems for different levels of
climate change, Global Environmental Change 14, 219-228.

Note: This story has been adapted from a news release issued by Centre
for International Climate and Environmental Research.

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Contact: editor@removeme.sciencedaily.com

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“The most likely way the climate could be influenced by either natural
or artificial means seems to be through a trigger mechanism that
ultimately changes the radiation balance …. Still another
possibility would be a change in the relative proportion of
atmospheric gases … the burning of fossil fuels would presumably
lead to more absorption of long-wave terrestrial radiation in the
atmosphere and consequently to greater heating.” Abraham Oort. “The
Energy Cycle of the Earth,” Scientific American. September 1970

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