From time to time, there is discussion about whether the recent warming trend is due just to chance. We have heard arguments that so-called ‘random walk‘ can produce similar hikes in temperature (any reason why the global mean temperature should behave like the displacement of a molecule in Brownian motion?). The latest in this category of discussions was provided by Cohn and Lins (2005), who in essence pitch statistics against physics. They observe that tests for trends are sensitive to the expectations, or the choice of the null-hypothesis .
Greenhouse gases help seasonal predictions
) The conventional wisdom in meteorology has been that certain factors such as the complete oceanic state and the exact concentrations of greenhouse gases are of minor importance for a normal weather forecast. Moreover, whereas sea surface temperatures (SST) are important, the deep sea temperatures are believed to have little impact for predictions for the next few days. The reason is that the ocean reacts slowly to changes in the atmosphere (has much higher inertia and much higher heat capacity). Hence, the most important information needed for such a weather forecast is the atmospheric initial conditions, a description of what the atmosphere and the SST look like when the weather model starts computing the weather evolution.
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Climate Basics
Recently, Oxford University launched a new initiative called Climate.Basics. This Internet site provides a nice explanation and simple illustrations on what is meant by ‘climate’ and how the climate system works. The Climate.Basics site is a collaboration with the climateprediction.net project, which is the world’s largest climate prediction experiment. We think this is quite good, but as always, let us know if you think something could be explained better
Storms & Global Warming II
Earlier this year, we posted two discussions on the association between climate change and storms: Storms and Climate Change and Some recent updates. I will use the abbreviation TC here in the loose meaning of a tropical cyclone. These posts discussed the high number of TCs during the previous hurricane season and an essay on the relation between TCs and climate change. The uncertainty surrounding trends in storminess was underlined, and a point was being made about this subject being controversial. [Read more…] about Storms & Global Warming II
On record-breaking events
NASA’s Earth Observatory reports that there was a record low Arctic sea ice concentration in June 2005. There was a record-number of typhoons over Japan in 2004. In June, there were reports of a number of record-breaking events in the US. And on July 28, the British News paper The Independent reported on record-breaking rainfall (~1 m) in India, claiming hundreds of lives. These are just a few examples of recent observations. So, what is happening?
A critique on Veizer’s Celestial Climate Driver
In a paper in Geoscience Canada, Veizer (2005) states that ‘the multitude of empirical observations favours celestial phenomena as the most important driver of terrestrial climate on most time scales‘. This paper was cited by a contributor to a debate on the website openDemocracy . In short, the argument is that the cosmic ray flux (CRF, also denoted as ‘GCR’ – galactic cosmic rays – in some papers) is the most important factor affecting our climate. Since this issue is likely to crop up from time to time, it is worth taking a closer look at the Veizer (2005) paper ( Here is a link to short summary, but the actual paper requires subscription). [Update: The actual paper is now available as supplemental material on the Geoscience Canada website.] I will try to show that CRF explanation for the recent global warming is easy to rule out.
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Storms and Climate Change
The Atlantic hurricane season will soon be upon us again , and no doubt many people will recall last year’s devastating Hurricanes that swept across Florida. There was a great deal of press about these storms, as 3 major hurricanes and 5 tropical storms made landfall in the US. According to HurricaneProtection.com, the last time eight different tropical cyclones impacted the United States coastline in a single season was 1916. There were a total of 15 tropical storms and hurricanes, which means that the total number of storms that year was higher than 95% of the previous years of hurricane observations. There was also a record number of Typhoons over Japan in 2004 (10! The previous record was 6 from 1996) . Typhoons are the same as Hurricanes, but have a different name over the Indian ocean and the western Pacific. They are also known as ‘tropical cyclones’. Furthermore, it was the first time that a tropical cyclone had been observed in the south Atlantic (see WMO Climate News, Jan 2005, p. 12)! So, what’s going on?
IPCC in action: Part II
The primary purpose of the Intergovernmental Panel for Climate Change (IPCC) is to assess the available scientific knowledge about climate change, not to initiate new research. The next IPCC report (Assessment Report 4, or AR4) is due in 2007, and in order to update of the state of knowledge it will only consider papers published in peer-review scientific journals between 2000 and papers submitted by May 1st 2005 (must be accepted before December 2005). It is essential that the papers be published in scientific quality journals in order to ensure the credibility of the results. Nevertheless the IPCC reports undergo several additional reviews and revisions involving a large number of independent referees. Thus, the IPCC reports undergo a more stringent review process than common papers in the scientific literature.
Are Temperature Trends affected by Economic Activity?
In a recent paper, McKitrick and Michaels (2004, or “MM04”) argue that non-climatic factors such as economic activity may contaminate climate station data, and thus, may render invalid any estimates of surface temperature trends derived from these data. They propose that surface temperature trends may be linked to various local economic factors, such as national coal consumption, income per capita, GPD growth rate, literacy rates, and whether or not temperature stations were located within the former Soviet Union. If their conclusions were correct, this would hold implications for the reliability of the modern surface temperature record, an important piece of evidence indicating 20th century surface warming. However, numerous flaws with their analysis, some of them absolutely fundamental, render their conclusions invalid.
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Rasmus E. Benestad
I am a physicist by training and have affiliations with the Norwegian Meteorological Institute [My views here are personal and may not necessarily represent those of Met Norway]. I have a D.Phil in physics from Atmospheric, Oceanic & Planetary Physics at Oxford University in the United Kingdom.
Recent work involve a good deal of statistics (empirical-statistical downscaling, trend analysis, model validation, extremes and record values), but I have also had some experience with electronics, cloud micro-physics, ocean dynamics/air-sea processes and seasonal forecasting. In addition, I wrote the book ‘Solar Activity and Earth’s Climate’ (2002), published by Praxis-Springer, and together with two colleagues the text book ‘Empirical-Statistical Downscaling’ (2008; World Scientific Publishers). I have also written a number of R-packages for climate analysis posted http://cran.r-project.org.
I was a member of the council of the European Meteorological Society for the period (2004-2006), representing the Nordic countries and the Norwegian Meteorology Society, and have served as a member of CORDEX Task Force on Regional Climate Downscaling.
In my work, I often get questions from media and lay persons about climate change. I believe it is necessary to approach these questions with identifying what we really don’t know and what we are more sure about. I believe that some of Karl Popper ideas about falsification can be useful.