Where Climate Change May Be Most Prominent In The 21st Century - GRL

[hatrack]

Baettig, Michèle B.; Wild, Martin; Imboden, Dieter M.

<1> A Climate Change Index (CCI) is developed that is composed of annual and seasonal temperature and precipitation indicators. These indicators are aggregated to a single index that is a measure for the strength of future climate change relative to today's natural variability. The CCI does not represent climate impacts. Its aim is to comply with the increasing need of policy makers to gain a quick overview of complex scientific findings by means of summarized information. The index is calculated on the basis of three GCM simulations of the 21st century under the IPCC emission scenarios A2 and B2. The results indicate that the strongest climate changes by the end of the 21st century, relative to today's natural variability, will occur in the tropics and in high latitudes (especially in the northern hemisphere). The CCI is also calculated on a country basis, allowing for comparison with social and economic country indicators.

EDIT


Figure 1. Individual CCI-indicators. Each indicator is a multi model ensemble mean of the two IPCC SRES scenarios A2 and B2. Changes refer to the control period 1961–1990 and the scenario period 2071–2100. Enhanced EPS <7.8 MB>


Figure 2. The aggregated CCI in two versions: (a) on a grid basis and (b) on a country basis. The country value is the mean of all grid values over the surface area of each country. Enhanced EPS <3.6 MB>

<21> In Figure 2 we present the aggregated Climate Change Index. Figure 2a shows the CCI on a grid basis. The values are between 3.8 and 10.7 additional strong climate events, with most lying between 5 and 9. The CCI indicates that climate will change most strongly relative to today's natural variability in the high latitudes and the tropics. The effect in the high latitudes has been reported by many others . In the CCI, this effect results mainly from an increase in extremely wet years and seasons, but also from an increase in annual temperatures. The high CCI-values in the tropics are caused by precipitation changes but also seasonal temperature events. Although several authors have reported strong tropical precipitation changes , this effect has not attracted much attention until today. Concerning strong temperature changes, it has to be noted that in the tropics the hot temperature indicator responds more strongly to absolute changes in mean than elsewhere, because natural temperature variability is much smaller in the tropics than in higher latitudes .

<22> In a recent study Giorgi <2006> presented a similar approach to calculate regional climate change hot-spots. He uses an index to compare climate change between different regions that, in contrast to our approach, is not relative to the natural variability. The Mediterranean and Northeastern Europe are identified as the most prominent hot-spots. In our study, these regions have an average CCI-value. According to both studies, climate will change strongly in high latitudes. The pronounced tropical changes predicted by the CCI are not identified by Giorgi, except for Central America. These differences may be explained by the above mentioned differences in indicators as well as by differences in GCM selection, analyzed time periods, weighting factors, and the level of aggregation.

<23> Figure 2b shows the average CCI for each country. The spatial aggregation of the data allows to compare the CCI with socio-economic country indicators. The Human Development Index (HDI) which is calculated on a country basis by the United Nations Development Programme is an index that is frequently used as a first approximation for vulnerability of countries towards climate change. Most African and some South East Asian countries have a low HDI and are therefore less capable to protect against and adapt to climate change. According to the CCI, climate is expected to change more strongly relative to today's natural variability in these more vulnerable countries than in many countries with a high HDI and thus lower vulnerability, such as the United States, European states and Australia. This general observation is supported by the correlation between the HDI and the CCI which is −0.25.

EDIt

No link, subscription service.