Uncertain climate models impair long-term climate strategies

September 19, 2011

A new paper published in Philosophical Transactions of the Royal Society A, explains weaknesses in our understanding of climate change and how we can fix them. These issues mean predictions vary wildly about how quickly temperatures will rise. This has serious implications for long term political and economic planning. The paper's lead author is Dr Nigel Fox of The National Physical Laboratory, The UK's National Measurement Institution.

The Earth's climate is undoubtedly changing, but how fast and what the implications will be are unclear. Our most reliable models rely on data acquired through a range of complex measurements. Most of the important measurements - such as ice cover, , sea levels and temperature, chlorophyll (oceans and land) and the radiation balance (incoming to outgoing energy) – must be taken from space, and for constraining and testing the forecast models, made over long timescales. This presents two major problems.

Firstly, we have to detect small changes in the levels of radiation or reflection from a background fluctuating as a result of natural variability. This requires measurements to be made on decadal timescales – beyond the life of any one mission, and thus demands not only high accuracy but also high confidence that measurements will be made in a consistent manner.

Secondly, although the space industry adheres to high levels of quality assurance during manufacture, satellites, particularly optical usually lose their calibration during the launch, and this drifts further over time. Similar ground based instruments would be regularly calibrated traceable to a primary standard to ensure confidence in the measurements. This is much harder in space.

The result is varying model forecasts. Estimates of global increases by 2100, range from ~2-10◦C. Which of these is correct is important for making major decisions about mitigating and adapting to : for instance how quickly are we likely to see serious and life threatening droughts in which part of the world; or if and when do we need to spend enormous amounts of money on a new Thames barrier. The forecasted change by all the models is very similar for many decades only deviating significantly towards the latter half of this century.

Dr Nigel Fox, head of Earth Observation and Climate at NPL, says: "Nowhere are we measuring with uncertainties anywhere close to what we need to understand climate change and allow us to constrain and test the models. Our current best measurement capabilities would require >30 yrs before we have any possibility of identifying which model matches observations and is most likely to be correct in its forecast of consequential potentially devastating impacts. The uncertainties needed to reduce this are more challenging than anything else we have to deal with in any other industrial application, by close to an order of magnitude. It is the duty of the science community to reduce this unacceptably large uncertainty by finding and delivering the necessary information, with the highest possible confidence, in the shortest possible time."

The solution put forward by the paper is the TRUTHS (Traceable Radiometry Underpinning Terrestrial- and Helio- Studies) mission, a concept conceived and designed at NPL. This which would see a satellite launched into orbit with the ability to not only make very high accuracy measurements itself (a factor ten improvement) but also to calibrate and upgrade the performance of other Earth Observation (EO) satellites in space. In essence it becomes "NPL in Space".

The TRUTHS satellite makes spectrally resolved measurements of incoming solar radiation and that reflected from the ground, with a footprint similar in size to half a rugby field. The unprecedented accuracy allows benchmark measurements to be made of key climate indicators such as: the amount of cloud, or albedo (Earth's reflectance) or solar radiation, at a level which will allow differences in climate models to be detected in a decade (1/3 that of existing instruments). Its data will also enable improvements in our knowledge of climate and environmental processes such as aerosols, land cover change, pollution and the sequestration of carbon in forests.

However, not only will it provide its own comprehensive and climate critical data sets but can also facilitate an upgrade in performance of much of the world's Earth observing systems as a whole, both satellite and ground data sets. By performing reference calibrations of other in-flight sensors through near simultaneous observations of the same target, it can transfer its calibration accuracy to them. Similarly its ability to make high accuracy corrections of atmospheric transmittance allow it to calibrate ground networks measuring changes at the surface e.g. flux towers and forests and other reference targets currently used by satellites such as snowfields of Antarctica, deserts, oceans and the Moon. In this way it can even back correct the calibration of sensors in-flight today.

TRUTHS will be the first satellite to have high accuracy traceability to SI units established in orbit. Its own measurements and in particular the calibration of other sensors will not only aid our understanding of climate change but also facilitate the establishment and growth of commercial climate and environmental services. One of the barriers to this markets growth is customer confidence in the results and long-term reliability of service. TRUTHS enable a fully interoperable global network of satellites and data with robust trustable guarantees of quality and performance.

The novelty of TRUTHS lies in its on-board calibration system. The instruments on the TRUTHS satellite will be calibrated directly against an on-board primary standard – an instrument called a CSAR (Cryogenic Solar Absolute Radiometer). This compares the heating effect of optical radiation with that of electrical power – transferring all the difficulties associated with existing space based optical measurements (drift, contamination, etc) to more stable electrical SI units. In effect, this mimicks the traceability chain carried out on the ground in orbit.

This would make climate ten times more accurate and give us models on which we could make important decisions about the future.

The project, which would be led by NPL, is being considered by different organisations. The European Space Agency has recommended looking into ways to take it forward, possibly as a collaboration with other space agencies. NASA is also keen to collaborate formally.

Nigel concludes: "Taking this forward would be an excellent investment for the UK, or any other country which supports it. This is not only an effective way to address the problem of understanding change, but also an excellent opportunity for business. It would grow expertise in Observation and showcase the UK's leading space expertise – an industry which is growing by 10 per cent a year. It would also provide a platform to underpin some of the carbon trading which will be a big international business in the near future."

The video will load shortly
Nigel Fox delivered a lecture on this subject as part of NPL's Celebrating Science lecture series

Explore further: UK satellite mission to improve accuracy of climate-change measurements gains global support

More information: Phil. Trans. R. Soc. A (2011) 369, 4028-4063 doi:10.1098/rsta.2011.0246

Related Stories

Satellites search out South Pole snowfields

January 13, 2009

As skiers across the world pay close attention to the state of the snow on the slopes, there are a different group of scientific snow-watchers looking closely at a South Pole snowfield this January.

Measuring salt shine to improve climate understanding

August 16, 2010

From 14 - 25 August 2010, scientists from around the world will gather in Southern Turkey to measure the spectral reflectance of a few square kilometres of salt. These measurements will have a major impact on the future of ...

Recommended for you

New findings on carbon cycle feed climate research

January 23, 2017

A Florida State University researcher is taking a deep dive into the carbon cycle and investigating how carbon moves from the ocean surface to greater depths and then remains there for hundreds of years.

Arctic melt ponds form when meltwater clogs ice pores

January 23, 2017

When spring comes to the Arctic, the breakup of the cold winter ice sheets starts at the surface with the formation of melt ponds. These pools of melted snow and ice darken the surface of the ice, increasing the amount of ...

Study finds parrotfish are critical to coral reef health

January 23, 2017

An analysis of fossilized parrotfish teeth and sea urchin spines by researchers at Scripps Institution of Oceanography at the University of California San Diego showed that when there are more algae-eating fish on a reef, ...


Adjust slider to filter visible comments by rank

Display comments: newest first

1.8 / 5 (10) Sep 19, 2011
doesn't sound like the truth the whole and nothing but the truth in the TRUTH.
3.4 / 5 (5) Sep 19, 2011
I can hear the denialists now... we know that climate change isn't real already, why waste more money proving it?

A closed mind isn't a terrible thing to waste.
2.3 / 5 (3) Sep 19, 2011
The title of the article seems a bit inflamitory and irresponsible. There's uncertainty in everything. Anyone who exagerates the uncertainty is no better than people who seek to trivialize it. Understanding the strengths and weaknesses of any specific model is important for the people who use them, but they know those weaknesses and they know the strengths. If they are ethical then they will temper their results based on those strengths and weaknesses. It's also not possible to talk about models in too general of terms. Each one is unique, made with different goals in mind and with different limitations of funding and resources.

The above is an interesting accademic exercise and a good topic for thought and discussion.

It's hardly a new topic though. The IPCC dedicates a section to this very topic, but in my opinion they could do a better job of doing a model by model breakdown of all the models they use. That would be more usefull than a blanket statement about all of the models
3 / 5 (2) Sep 19, 2011
One interesting thing I see right now in regard to models is the champaign problem of having too much new discovery to get it all programmed into the models as fast as they would like. With the recent bounty of new discoveries, it must be a nightmare for modelers to try to keep up with the pace and try to figure out ways to integrate all the new theories into their models. Knowing how something works and writing software to duplicate it are two different things. Then, as is usual with computer software, it's wise to test as you go before making too many changes, so that you have some idea where the problem lies when something blows up.
3 / 5 (2) Sep 19, 2011
Which of these is correct is important for making major decisions about mitigating and adapting to climate change: for instance how quickly are we likely to see serious and life threatening droughts in which part of the world;

I can't resist pointing out a bit of clever alarmism, though I despise the extreme denial as much as I despise this stuff:

a more balanced editorial might have said something more like: For instance, are we likely to see droughts or increased rainfall? And where, when, and how much?

You did realize that the part of the article I quoted was an editorial opinion, right?
1.4 / 5 (9) Sep 19, 2011
"Past climate change data from satellites have provided invaluable information, but have sometimes been challenged due to controversy related to the accuracy of the measurements. Technological advances of the past decade along with the increasing maturity of the areas of science that support space-based climate measurements, allow scientists to robustly implement SI traceable satellite observations today. By carefully learning from the successes and shortcomings of previous missions, the CLARREO mission looks to directly address the societal objectives of characterizing long-term climate change and testing climate projections to support public and private decision-making with the most reliable information possible. "
Which implies current data is less reliable.
2.5 / 5 (8) Sep 19, 2011
gee wouldnt want actual science getting in the way of 'The Science'.
I think its hilarious how governments can consider spending hundreds of billions of dollars due to modelling results without have first considered spending a couple billion dollars on satellites and measurements, given that the IPCC states that many of the forcing factors are poorly understood.

Of course if measurements were allowed to trump models Im not sure the alarmist position would last long, IMHO.
2.6 / 5 (9) Sep 19, 2011
Sound promising, nevertheless wrong, the Sun is the dominant power source, but other sources should not be neglected such as :
-Earth's radioactive core heat "generator"
-tidal forces
-Cosmic radiation sources.
These are significant influences on the climate
4.5 / 5 (2) Sep 19, 2011
Instruments without absolute accuracy are quite useful in discovering trends, which is, after all, what is troubling us. Calibration is important, but change is more important. If we demand absolute proof of smething, all we have to do is wait until it has happened.
1.4 / 5 (11) Sep 20, 2011
I recommend that they start by looking at new information on Earth's heat source - the violently unstable Sun [1-4]

1. NASA News (19 Sept 2011) "The secret lives of solar flares


2. "Neutron repulsion", The APEIRON Journal, in press (2011)


3. "Earth's Heat Source - The Sun", Energy and Environment 20, 131-144 (2009)


4. "Super-fluidity in the solar interior: Implications for solar eruptions and climate", Journal of Fusion Energy 21, 193-198 (2002):


With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo
1 / 5 (2) Sep 20, 2011
Opening sentence: "The Earth's climate is undoubtedly changing, ..." Or not. They've assumed the conclusion, and are now arranging the evidence to support it.
1 / 5 (4) Sep 20, 2011
Opening sentence: "The Earth's climate is undoubtedly changing, ..." Or not. They've assumed the conclusion, and are now arranging the evidence to support it.

That opening statement would be a good one for all studies of global climate change.


1. Earth's climate has always changed [1].
2. Earth's heat source is a variable star.
3. The Sun is violently unstable [2].
3. That is why life evolves [1].

[1] "Origin and Evolution of Life Constraints on the Solar Model",
Journal of Modern Physics 2, 587-594 (2011)


[2] See links posted above

With kind regards,
Oliver K. Manuel

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.