Understanding climate extremes: Journal Club with Dr Julie Jones

Extreme temperatures are one of the most important factors to considering when planning for a sustainable future. In this blog post, Grantham Scholar Monica Ortiz reflects on the Journal Club session led by one of her supervisors, Dr Julie Jones, which demonstrated the important role that climate data plays in all kinds of food security research.

This week’s paper

Detectable Changes in the Frequency of Climate Extremes‘ by S. Morak, G. C. Hegerl and N. Christidis.

monica-ortizExtreme climate events like droughts and heat waves can cause socioeconomic, health and environmental damage. They are projected to become more frequent as our world warms.[1]

For her Journal Club, Dr Julie Jones from the Department of Geography and the Grantham Scholars discussed ‘Detectable Changes in the Frequency of Climate Extremes‘ by S. Morak, G. C. Hegerl and N. Christidis [2], which Julie chose to emphasise the significance of the research behind climate extremes. In the work that used real-world climate observations, climate models and statistics, the researchers sought to answer the questions:

  1. Have there been changes to hot and cold extreme temperatures globally and regionally?
  2. Are these changes greater than could be expected due to “natural” or internal climate variability?

The Intergovernmental Panel on Climate Change (IPCC) in their Special Report on Extreme Events (SREX) reported that climate change leads to changes in the frequency, intensity, spatial extent, duration, and timing of extreme weather and climate events. Changes in temperature between present and future climate could mean (a) a shift towards a warmer climate, with less cold weather and less cold extremes; (b) no change to the mean temperature, but increases in climate variability, meaning more of both hot and cold extremes; or (c) a changed distribution where there may be changes to both the mean and the variability.

Because of these changes to the mean and/or the variability, including extremes, the discussed paper is relevant in the context of the Grantham Scholars’ research on food security. Shifting means and extreme hot or cold temperatures will have significant impacts on agriculture, particularly crop production. The scholars discussed the relevance of the work on their diverse fields of research – for example Emanga Alobwede shared that extreme temperature changes will have impacts on soil viability for agriculture in terms of soil moisture, microbial life and erosion. The attribution of extremes to anthropogenic greenhouse gases is also important to Stefano Gollinelli’s work on politics and governance as more proactive changes in land use and food security policies may be needed. The methodologies of detection and attribution in climate modelling have their cognates in the work of James Thackery and Hannah Sewell in finding which genes will lead to their desired outcomes (bigger seeds and drought tolerance, respectively).

An active discussion between the cohort and Julie led to interesting questions on the rather complex methodology of the research, including the importance of having long-term weather data. Ideally, there would be numerous weather stations that collect relevant climate data all over the world, which would help in building robust datasets for evaluation of the work that models do. James Thackery brought up the point that weather stations would be extremely useful in regions of high biodiversity like the Amazon. However, as Julie and the cohort discussed, in reality, countries may be constrained by their resources and infrastructure to have weather stations. For example, there are significantly fewer covered areas in the Southern Hemisphere and in many developing countries, including those in Sub-Saharan Africa.

Although there were some model simulations that significantly underestimated climate in particular regions, ultimately, the study found that there have been significant increases in warm extremes and decreases in cold extremes because of fewer cold days and nights and more warm days and nights in both hemispheres. Additionally, although the magnitude of the contribution of greenhouse gases was not covered by the work, the study found that greenhouse gas forcing has contributed to these observed changes.

The facts from this work and other related research are clear: the greenhouse gas emissions resulting from our rapid growth and development have adverse effects on our efforts for food security and sustainable development. These are important wake-up calls that we need to change the way we fuel our progress, not only for the sake of the most vulnerable but for all.


[1] Hegerl, G.C., Hanlon, H. and Beierkuhnlein, C. (2011). Elusive Extremes. Nature Geoscience. 4: 142-143.

[2] Morak, S., Hegerl, G.C., and N. Christidis. (2013). Detectable changes in the frequency of temperature extremes. Journal of Climate. 26: 1561-1574.