Is the CRU the 'principal source' of climate change projections?
In the wake of the illegal hacking of emails from the University
of East Anglia, climate skeptics
criticised the global temperature records jointly held by the
Climate Research Unit (CRU) at UEA with the UK Met Office - arguing
that the evidence that temperatures are rising is therefore
unreliable.
As has been profiled
both on
Skeptical Science and at Carbon Brief, there
are three principal surface temperature datasets, of which the
CRU/Met Office hold just one. Temperature datasets are just one
(important) part of our scientific understanding of climate
change.
Despite this, some climate skeptics claim that scientists at the
CRU or Met Office are responsible for the majority of projections
about what climate change will look like in the future.
This is typified by
this quote from the founder of the UK climate sceptic
think-tank the GWPF, Lord Nigel Lawson:
"the scientific basis for global warming
projections is now under scrutiny as never before. The principal
source of these projections is produced by a small group of
scientists at the Climatic Research Unit (CRU), affiliated to the
University of East Anglia."
Skeptics like to suggest that climate projections depends
entirely on the institution that they're currently attacking. It's
a technique to allow them to smear the whole of climate science
with the failings - real or imagined - of just one group.
For examples, see Christopher Booker's attack on CRU in the
Sunday
Telegraph, or skeptic blogger Richard North's attack on the Met
Office in the Daily Mail,
where he writes:
"The Met Office seems to have forgotten
what it was set up for - to predict weather day by day. Instead, it
is devoting its energies to the fantasy that it can predict climate
decades ahead when it cannot even tell you whether it is going to
snow next week, or whether we might have a barbecue summer."
In reality, of course, climate
projections are not just produced by the Climatic Research Unit or
the Met Office. The
IPCC fourth assessment report, published in 2007, used climate
projections produced
by 16 modelling groups, from 11 countries, using 23 models.
Even more researchers are involved in the IPCC 5th Assessment
Report (due to be published in 2014), with 20 modelling groups from
all around the world working on it so far.
The AR4 climate projections
were based on greenhouse gas emissions scenarios that depict how
the future might unfold, depending on how emissions and their
causes change in the future. The scenarios consider changes in
population, economics and the development of new technologies. The
different scenarios are outlined in the
Special Report on Emission Scenarios, developed by the IPCC
(see graph below).
Atmospheric CO2 concentrations as observed at
Mauna Loa from 1958 to 2008 (black dashed line) and projected under
the 6 IPCC emission scenarios (solid coloured lines). (IPCC Data Distribution
Centre)
All of the climate model output
used in AR4 is available
online, resulting (at the time of writing) in 575 peer-reviewed
publications, both using and critiquing the data.
So how much does our
understanding of climate change depend on the CRU? They provide
climate models and a number of datasets to the climate science
community, including records of changes in surface temperature
since 1850. These show good agreement with other temperature
records such NASA's
Goddard Institute of Space Studies (GISS) and NOAA's National
Climatic Data Centre (NCDC).
Using a
combination of models from many different research groups
allows the IPCC scientists to more successfully reproduce features
of earth's current climate than by using only a single
model.
Comparing the ability of models
to reproduce past and current climate change with observational
data also allows the uncertainties in climate projections to be
assessed.
In summary, it is the combined
work of scientists from many different parts of the world which
produces projections for the future impacts of climate change.
These projections are complicated and time-consuming to produce, as
they are dependent on so many unknown factors - how societies and
economies will develop, where we will get our energy from, the
unknowns in how the earth and atmosphere will respond to rising
greenhouse gases, and the limitations of computer models (something
we will discuss in a future post). Many scientists around the world
- rather from just one or two institutions - are working together
to try and reduce these uncertainties and increase our
understanding of the future impacts of climate change.