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About Rasmus Benestad

I am a senior scientist working at the Norwegian Meteorological Institute with a background from physics. My scientific career started with a degree in Physics with Electronics at UMIST in Manchester (UK), cloud micro-physics at New Mexico Tech (USA), and ocean physics at Atmospheric Oceanic and Planetary Physics (AOPP) at Oxford University (UK). Since then, I have also got heavily involved in the field of statistics, thanks to exciting collaborations with several statisticians.

My primary focus at the Norwegian Meteorological Institute has been towards climate change adaptation, empirical-statistical downscaling and anthropogenic climate change, but I have also worked on problems relating to natural climate variations connected to changes in the sun. I have authored two text books on these topics: Solar Activity and Earth's climate (Praxis/Springer) and Empirical-Statistical Downscaling (World Scientific Publishers).

My experience from the climate science community includes several roles: a contributing author on two past IPCC assessment reports, a person of contact (POC) for World Climate Research Programme's (WCRP) CORDEX project, a coordinating lead author on Arctic Monitoring and Assessment Programme's (AMAP) report Adapting Actions in a Changing Arctic (AACA, 2017), a councilor for the European Meteorological society (EMS), a member of the EMS communication and media committee, and part of the advisory board for Oxford Research Encyclopedia on climate. I also chair the professional network within the Norwegian trade union for engineer and natural scientists Tekna Klima, dealing with a diverse range of climate solutions.

Cosmic rays don’t die so easily

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Cover picture of Solar Activity and Earth's Climate Last week, a Norwegian official-looking – and in my view – climatesceptic website praised Eigil Friis-Christensen from the Danish space center (featuring in the Great Global Warming Swindle) and hailed him for having given the best speech ever in the annual Birkeland seminar organized by Norwegian Academy of Science and Letters (NASL). There were rumours of controversy behind the scene before the seminar, as the NASL is regarded as a prestigious body in Norway.

Furthermore, Svensmark and Friis-Christensen have written a response (title ‘Reply to Lockwood and Fröhlich – The persistent role of the Sun in climate forcing’; DNSC Scientific Report Series 3/2007) to a recent paper by Lockwood and Frohlich (LF2007). In this response, they state ’… [LF2007] argue that this historical link between the Sun and climate came to an end about 20 years ago‘. Another quote from their response is ‘Here we rebut their argument comprehensively’. So the cosmic ray theory isn’t quite dead after all?

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Regional Climate Projections

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Regional Climate Projections in the IPCC AR4

glasses How does anthropogenic global warming (AGW) affect me? The answer to this question will perhaps be one of the most relevant concerns in the future, and is discussed in chapter 11 of the IPCC assessment report 4 (AR4) working group 1 (WG1) (the chapter also has some supplementary material). The problem of obtaining regional information from GCMs is not trivial, and has been discussed in a previous post here at RC and the IPCC third assessment report (TAR) also provided a good background on this topic.

The climate projections presented in the IPCC AR4 are from the latest set of coordinated GCM simulations, archived at the Program for Climate Model Diagnosis and Intercomparison (PCMDI). This is the most important new information that AR4 contains concerning the future projections. These climate model simulations (the multi-model data set, or just ‘MMD’) are often referred to as the AR4 simulations, but they are now officially being referred to as CMIP3.

One of the most challenging and uncertain aspects of present-day climate research is associated with the prediction of a regional response to a global forcing. Although the science of regional climate projections has progressed significantly since last IPCC report, slight displacement in circulation characteristics, systematic errors in energy/moisture transport, coarse representation of ocean currents/processes, crude parameterisation of sub-grid- and land surface processes, and overly simplified topography used in present-day climate models, make accurate and detailed analysis difficult.

I think that the authors of chapter 11 over-all have done a very thorough job, although there are a few points which I believe could be improved. Chapter 11 of the IPCC AR4 working group I (WGI) divides the world into different continents or types of regions (e.g. ‘Small islands’ and ‘Polar regions’), and then discusses these separately. It provides a nice overview of the key climate characteristics for each region. Each section also provides a short round up of the evaluations of the performance of the climate models, discussing their weaknesses in terms of reproducing regional and local climate characteristics.

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Transparency of the IPCC process

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Recently, a Financial Times op-ed criticised the IPCC for having contributors and peers drawn from a narrow professional circle. I don’t think this is fair, unless one regards a whole discipline as ‘narrow’. Furthermore, recent public disclosure of both comments and response suggests a different story to the allegations in the FT op-ed of ‘refusing to disclose data and methods’. The IPCC has no control over the independent publication, but the disclosure of the comments and response at least enhances the openness for the synthesis of the report.

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Why global climate models do not give a realistic description of the local climate

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Translations: (Português)

Global climate
glasses Global climate statistics, such as the global mean temperature, provide good indicators as to how our global climate varies (e.g. see here). However, most people are not directly affected by global climate statistics. They care about the local climate; the temperature, rainfall and wind where they are. When you look at the impacts of a climate change or specific adaptations to a climate change, you often need to know how a global warming will affect the local climate.

Yet, whereas the global climate models (GCMs) tend to describe the global climate statistics reasonably well, they do not provide a representative description of the local climate. Regional climate models (RCMs) do a better job at representing climate on a smaller scale, but their spatial resolution is still fairly coarse compared to how the local climate may vary spatially in regions with complex terrain. This fact is not a general flaw of climate models, but just the climate models’ limitation. I will try to explain why this is below.

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Does a Global Temperature Exist?

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Translations: (Português)

Does a global temperature exist? This is the question asked in a recently published article in Journal of Non-Equilibrium Thermodynamics by Christopher Essex, Ross McKitrick, and Bjarne Andresen. The paper argues that the global mean temperature is not physical, and that there may be many other ways of computing a mean which will give different trends.

The common arithmetic mean is just an estimate that provides a measure of the centre value of a batch of measurements (centre of a cloud of data points, and can be written more formally as the integral of x f(x) dx. The whole paper is irrelevant in the context of a climate change because it missed a very central point. CO2 affects all surface temperatures on Earth, and in order to improve the signal-to-noise ratio, an ordinary arithmetic mean will enhance the common signal in all the measurements and suppress the internal variations which are spatially incoherent (e.g. not caused by CO2 or other external forcings). Thus the choice may not need a physical justification, but is part of a scientific test which enables us to get a clearer ‘yes’ or ‘no’. One could choose to look at the global mean sea level instead, which does have a physical meaning because it represents an estimate for the volume of the water in the oceans, but the choice is not crucial as long as the indicator used really responds to the conditions under investigation. And the global mean temperature is indeed a function of the temperature over the whole planetary surface.

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‘Cosmoclimatology’ – tired old arguments in new clothes

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Translations: (Português)

Image from cosmosIn a recent issue of the journal Astronomy and Geophysics (A&G), Henrik Svensmark coined a new term: ‘cosmoclimatology’ . I think ‘cosmoclimatology’ is a good and refreshing name for anything combining our cosmos with our climate. However, all other aspects of the article I found very disappointing. We have already covered most of these topics before, but the A&G articles provides us with some new aspects to discuss. Furthermore, Svensmark is the Director for Center for Sun-Climate Research, Danish National Space Center, and therefore influential. He is also the co-author of a recent book with Nigel Calder that received some attention. Furthermore, a laboratory experiment of his also managed to make some headlines. It seems that solar forcing is one of the sceptics’ last trenches in the debate about climate change. In my view the A&G paper therefore merits a comment as long as the same old and worn arguments resurface without discussing misgivings from the critics.

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Climate Reporting in Physics World

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Translations: (Português)

PhysicsWorld cover, Volume 20, no. 2, February 2007 The February 2007 issue of PhysicsWorld contains several articles relevant to climate research, with a main feature article on climate modelling written by Adam Scaife, Chris Folland, and John Mitchell, and a profile on Richard Lindzen as well as an article on geoengineering in the ‘News & Analyses’ section. The magazine also contains an article (‘Living in the greenhouse’) under ‘Lateral Thoughts’ that brings up a bunch of tentative analogies to a wide range of topics completely unrelated to the greenhouse effect in a technical sense, and an editorial comment ‘Hot topic‘, arguing that it would be wrong of PhysicsWorld to ignore those outside the mainstream. To be more precise, the editorial comment devotes a few lines justifying the profile on Lindzen and the report on geoengineering, with a reference to a Feynman quote: “There is no harm in doubt and scepticism, for it is through these that new discoveries are made”. Wise words! Nevertheless, I cannot resist making some reflections.

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What triggers ice ages?

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Translations: (Português) (Türkçe) (Français)

by Rasmus Benestad, with contributions from Caspar & Eric

In a recent article in Climatic Change, D.G. Martinson and W.C. Pitman III discuss a new hypothesis explaining how the climate could change abruptly between ice ages and inter-glacial (warm) periods. They argue that the changes in Earth’s orbit around the Sun in isolation is not sufficient to explain the estimated high rate of change, and that there must be an amplifying feedback process kicking in. The necessity for a feedback is not new, as the Swedish Nobel Prize winner (Chemistry), Svante Arrhenius, suggested already in 1896 that CO2 could act as an amplification mechanism. In addition, there is the albedo feedback, where the amount of solar radiation that is reflected back into space, scales with the area of the ice- and snow-cover. And are clouds as well as other aspects playing a role.

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On Mid-latitude Storms

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Statements often appear in the media about suggesting that more extreme mid-latitude storms will result from global warming. For instance, western Norway was recently battered by an unusually strong storm which triggered many such speculations. But scientific papers on how global warming may affect the mid-latitude storms give a more mixed picture. In a recent paper by Bengtsson & Hodges (2006), simulations with the ECHAM5 Global Climate Model (GCM) were analysed, but they found no increase in the number of mid-latitude storms world-wide. Another study by Leckebusch et al. (2006) showed that the projection of storm characteristics was model-dependent. (Note that the dynamics of tropical and mid-latitude (often called ‘extra-tropical’) storms involve different processes, and tropical storms have been discussed in previous posts here on RC: here, here, here, and here).

The factors that control this are often confounding and so make this a tricky prediction. Simple arguments based on the expected ‘polar amplification‘ and the fact that the surface temperature gradient between the tropics and the poles will likely decrease would reduce the scope for ‘baroclinic instability’ (the main generator of mid-latitudes storms). However, there are also increases in the upper troposphere/lower stratospheric gradients (due to the stratosphere cooling and the troposphere warming) and that has been shown to lead to increases in wind speeds at the surface. And finally, although latent heat release (from condensing water vapour) is not a fundamental driver of mid-latitude storms, it does play a role and that is likely to increase the intensity of the storms since there is generally more water vapour available in warmer world. It should also be clear that for any one locality, a shift in the storm tracks (associated with phenomena like the NAO or the sea ice edge) will often be more of an issue than the overall change in storm statistics.
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Not just ice albedo

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Translations: (Français)

A recent paper by Francis & Hunter provides an interesting discussion about reasons for the recent decline in the Arctic sea-ice extent, based on new satellite observations. One common proposition about sea ice is that it involves a positive feed-back because the ice affects the planetary albedo (how the planet reflects the sunlight back to space before the energy enters the ‘climate system’). Yet, there is more to the story, as the ice acts more-or-less like an insulating lid on top of the sea. There are subtle effects such as the planet losing more heat from the open sea than from ice-covered region (some of this heat is absorbed by the atmosphere, but climates over ice-covered regions are of more continental winter character: dry and cold). The oceanic heat loss depends of course on the sea surface temperature (SST). Open water also is a source of humidity, as opposed to sea-ice (because its cold, not because its dry), but the atmospheric humidity is also influenced by the moisture transport associated with the wind (moisture advection). Francis & Hunter found a positive correlation between lack of ice and the downward long-wave radiation, something they attributed primarily to cloudiness. Hence, clouds play a role, both in terms of influencing the albedo as well as trapping out-going heat. Francis & Hunter suggest that the changes in the long-wave radiation is stronger than the clouds’ modulation of the direct sunlight.
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