Climate Models and Living Species

“We have to try to model an immensely complex
system all the way from the tropical rainforest,
the oceans, the northern hemisphere forests, the
soil – and we have no fundamental equations to do
that with,” he says.

“When we are modelling the physics of the oceans
and the atmosphere, we do have some fundamental

“We don’t have those for the living parts of the system.”

Published: 2008/05/06 08:12:52 GMT

Climate prediction: No model for success
By Roger Harrabin
Environment analyst, BBC News

Pier Luigi Vidale smiles fondly as he gazes at
the image unfolding on his screen.

It is a rare and beautiful view of Planet Earth.

Curlicues of cloud formations swirl around the
Antarctic at the bottom of the screen as if
captured by time-lapse photography.

The image resembles a view of the Earth from space, stretched full frame.

But a small yellow ball scudding along the bottom
of the screen hints at another story.

The ball is the Sun, heating the surface as it
passes and provoking a daily puff of cloud from
the Amazon rainforest in this computer-generated
climate model.

The animation comes from research led by Dr
Vidale at Reading University’s Walker Institute.

It is designed to provide long-term data to help
scientists distinguish between heating trends and
natural climatic fluctuations.

This week, about 150 of the world’s top climate
modellers have converged on Reading for a four
day meeting to plan a revolution in climate

And they have plenty of work to do. So far
modellers have failed to narrow the total bands
of uncertainties since the first report of the
Intergovernmental Panel on Climate Change (IPCC)
in 1990.

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Vicky Pope from the Met Office explains how
climate models have changed over the years

And Julia Slingo from Reading University admitted
it would not get much better until they had
supercomputers 1,000 times more powerful than at

“We’ve reached the end of the road of being able
to improve models significantly so we can provide
the sort of information that policymakers and
business require,” she told BBC News.

“In terms of computing power, it’s proving
totally inadequate. With climate models we know
how to make them much better to provide much more
information at the local level… we know how to
do that, but we don’t have the computing power to
deliver it.”

Professor Slingo said several hundred million pounds of investment were needed.

“In terms of re-building something like the
Thames Barrier, that would cost billions; it’s a
small fraction of that.

“And it would allow us to tell the policymakers
that they need to build the barrier in the next
30 years, or maybe that they don’t need to.”

Knowing the unknowns

One trouble is that as some climate uncertainties
are resolved, new uncertainties are uncovered.

Some modellers are now warning that feedback
mechanisms in the natural environment which
either accelerate or mitigate warming may be even
more difficult to predict than previously assumed.

Research suggests the feedbacks may be very
different on different timescales and in response
to different drivers of climate change.

Just last week, preliminary research at the
Leibniz Institute of Marine Sciences in Kiel,
Germany, suggested that natural variations in sea
temperatures will cancel out the decade’s 0.3C
global average rise predicted by the IPCC, before
emissions start to warm the Earth again after

IPCC authors said this was not incompatible with
their models; but the German research provoked
some sceptics to ask whether models could be
believed at all.

“If we ask models the questions they are capable
of answering, they answer them reliably,”
counters Professor Jim Kinter from the Center for
Ocean-Land-Atmosphere Studies near Washington DC,
who is attending the Reading meeting.

“If we ask the questions they’re not capable of
answering, we get unreliable answers.”

Natural wobbles

Models work by simulating the multitude of
influences on the climate, including the Sun, the
Earth’s orbital wobbles, volcanoes, ocean
currents, rainforests and man-made pollution.

The modellers draw on science to create equations
which, once inside the computer, project a
picture of the future climate.

All the models used in the IPCC’s vast report
last year forecast warming of at least 2C if CO2
doubles (up from a 1.5C minimum rise in the
organisation’s 2001 report).

This warming is predicted to increase some crop
yields in northern countries, but also bring more
floods and droughts – particularly in poor

Double or even triple pre-industrial CO2 levels
are inevitable by the end of the century unless
emissions are very radically cut.

Many scientists believe that exceeding a 2C rise
would substantially increase the risk of causing
irreversible feedbacks.

Significantly, most IPCC models suggest a rise of 3C if CO2 doubles.

This is forecast to cause increased droughts for
more than a billion people, bring about
widespread death of coral reefs, and put up to a
third of all species at risk of extinction.

The most extreme IPCC model projects over 7C, and
other models indicate that rises of double
figures are possible.

The models paint a big picture. They struggle to
capture regional detail and precipitation; none
can successfully forecast the eminently
predictable daily rainfall in the Amazon, for

Professor Slingo emphasises the importance of
having good information on rainfall in a world
hungry for more food.

Cycles of life

Differences between high and low projections in
climate models used by the IPCC stem mainly from
uncertainties over feedback mechanisms – for
example, how the carbon cycle and clouds will
react to future warming.

Roger Harrabin explains how cloud feedback works

If clouds trap more heat or the planet releases
more carbon, then climate change may accelerate

If clouds reflect heat or the planet takes up
carbon, we could get away with higher CO2
Carbon cycle feedback explained

Professor Andrew Watson at the University of East
Anglia researches carbon uptake in the oceans.

He fears dangerous climate change; but he told
BBC News that basic science on the carbon cycle
is too poorly understood to make a meaningful
contribution to models.

“We have to try to model an immensely complex
system all the way from the tropical rainforest,
the oceans, the northern hemisphere forests, the
soil – and we have no fundamental equations to do
that with,” he says.

“When we are modelling the physics of the oceans
and the atmosphere, we do have some fundamental

“We don’t have those for the living parts of the system.”

Cloudy view

Clouds are the biggest “known unknown”. Those
with low tops bounce the Sun’s energy back into
space to keep us cooler, whereas high-level
clouds tend to trap heat radiating upwards from
the Earth.

The crucial question is which sort of clouds will
be favoured in the warmer world most scientists

All but one of the IPCC models predict that
clouds will accelerate future warming.

Professor Roy Spencer, a meteorologist from the
University of Alabama at Huntsville and a noted
critic of the IPCC, accepts that this forecast
may be right – but believes that the opposite
will prove true.

He thinks clouds are impossible to model at present.

“We just haven’t had very good data for more than
about six years pertaining to clouds,” he says.

“And obviously climate change is a multi-decade
or a century-timescale kind of thing.

“We would’ve needed really good cloud
observations for the last 50 years to know how
clouds affect climate.”

Pier Luigi Vidale says modellers are learning
fast about clouds, which respond instantly to
changing temperatures.

They say many cloud feedback uncertainties are
factored into their projections, which have been
tacitly accepted by the world’s leading
governments which control the IPCC.

Political leaders have now agreed that they
cannot wait for the modelling uncertainties to be
ironed out.

They have said they are convinced that emissions
should be cut; but they just cannot agree who
should do it.


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