Over the past decades, a continuous rise in global air temperatures resulted in significant changes in the global hydrological cycle. Regionally increased frequencies of extreme weather events and changes in the regional extent of drylands resulted in new areas at risk of desertification, a complex process driven by socio‐economic and climate‐related factors. Although desertification is not confined to drylands, they are the most vulnerable to land degradation processes. To investigate possible changes in climate patterns over the past 60 years, we couple the information obtained from the Köppen–Geiger (KG) climate classification and the FAO aridity index (AI), providing an overview of the most evident global changes in climate regimes from 1951–1980 to 1981–2010 and focussing on the modifications of the extent of drylands. KG and AI indicators have been computed on a 0.5° × 0.5° global grid using precipitation data from the Full Data Reanalysis (v6.0) of the Global Precipitation Climatology Centre, and mean temperature and potential evapotranspiration data from the Climate Research Unit of the University of East Anglia (CRUTSv3.20). Both KG and AI show that the arid areas globally increased between 1951–1980 and 1981–2010, but decreased on average in the Americas. North‐Eastern Brazil, Southern Argentina, the Sahel, Zambia and Zimbabwe, the Mediterranean area, North‐Eastern China and Sub‐Himalayan India have been identified as areas with a significant increase of drylands extent. An analysis of the scientific literature gives evidence that most of the areas identified are effectively undergoing desertification, thus confirming the validity of AI and KG to highlight the areas under risk of desertification. We also discuss the global decrease of cold areas, the progressive change from continental to temperate climate in Central Europe, the shift from tundra to continental climate in Alaska, Canada and North‐Eastern Russia and the widening of the tropical belt.

IISD news
22 October 2014: A study by the Joint Research Centre of the European Commission (JRC) has identified areas in South America, Africa and Asia at climatological risk of desertification. The study, which used information from two indexes, found significant shifts in climate zones resulting from changes in the global hydrological cycle. As a result, arid areas have increased by 1.4-3.4% globally.

The study, titled ‘Towards identifying areas at climatological risk of desertification using the Koppen-Geiger classification and FAO aridity index,’ and published in the International Journal of Climatology, analyzes spatial changes in climate indicators over the past six decades using information from the Koppen-Geiger (KG) climate classification and the FAO aridity index (AI).

The report highlights significant shifts in climate zones at both global and continental scales over past decades, and more specifically, the report finds that: a continuous rise in global temperatures has led to changes in the global hydrological cycle; cold areas have decreased, while arid areas globally have increased, with the exception of the Americas; regional changes in the extent of drylands have prompted the emergence of new areas at risk of desertification; and arid areas have increased worldwide, and in particular in Europe, Africa and China.

The study identifies as hotspots, or areas at high desertification risk, Northeastern Brazil, Southern Sahel, Zambia and Botswana, Southern Spain, Northeastern China, Central India and Southern Argentina. Furthermore, it discusses the widening of the tropical belt and shifts from: continental to temperate climate in Central Europe; and tundra to continental climate in Alaska, Canada and Northeastern Russia.