Thursday 30 March 2017
Projection results of the regional climate models for the Carpathian Basin

The regional climate models applied at the Hungarian Meteorological Service (ALADIN-Climate and REMO) are different not only in terms of applied numerical schemes and physical parameterization processes, but also in many respects of their simulations (Tables 1 and 2). Nevertheless, all the projections are focusing on the climate change over the Carpathian Basin for the 21st century, therefore, the common (ensemble) evaluation of the results can give a hint for the extent of climate change and the related uncertainties. If the two models project similar changes, the certainty is higher, while in the opposite case when the results are contradicting, the common interpretation should be more careful and more emphasis should be put on the uncertainties. Hereafter projection results for temperature and precipitation (annual and seasonal mean values for both models) are shown for two future periods (2021-2050 and 2071-2100) with respect to the reference period (1961-1990). It is emphasised that climate change signals are determined on the basis of differences between the (future) projection and (past) reference periods in order to avoid the possible systematic model errors (this approach assumes that model error characteristics remain the same for the past and future periods).

Temperature

The two regional climate models "agree" in the increase of the mean temperature during the 21st century in the Carpathian Basin (Fig. 1): this statement is valid for all seasons, moreover, in a statistically significant way for every period (i.e., the inter-annual variability is smaller than the degree of the change). The increase is continuous in the sense that for 2071-2100 its value is larger (3.5 degree in average) than for 2021-2050 (1.7 degree in average). Certainly, it does not mean that all the forthcoming years in the future will be warmer than the reference period: in spite of the positive trend cooler years and seasons can be anticipated, as well. There is a difference between the precise warming values of the two models, especially when considering the seasonal tendencies. The largest departure between the two models is for summer in the period of 2021-2050 between 1.4 and 2.6 degrees, while for 2071-2100 the same values are 4.1-4.9 degrees. The spatial details of the projections show (in agreement of the two models) that the temperature increase will be larger in the Eastern and Southern parts of the country.

Precipitation

The precipitation change results are much less clear, since the models mostly "disagree" even in the sign of the changes (which are mostly not significant on top of that). For 2021-2050 the models are in agreement regarding the unchanged amount of annual precipitation and in the slight summer decrease (5-10%; Fig. 2). At the same time, there are also such areas (especially over the Northern regions) where both models indicate slight summer precipitation increase. For spring and winter the RCMs provide rather different projections: less than 10% increase and decrease are equally possible for both seasons.

For the end of the century both models render a slight annual precipitation decrease, which is around 5%. The main directions of changes simulated for the middle part of the century are going to continue with different amplitudes, though. The summer precipitation decrease can exceed 20% on average for Hungary. In winter one model shows the possibility of 5% decrease, while the other one projects 30% increase. (Otherwise, the enhanced amount of winter precipitation is confirmed by the lower resolution RCM results of the former European PRUDENCE project).

1. ábra

Figure 1: Annual and seasonal mean temperature changes (°C) based on the two applied regional climate models
for the periods of 2021-2050
and 2071-2100 with respect to the mean values of 1961-1990

2. ábra

Figure 2: Annual and seasonal relative precipitation changes (%) based on the two applied regional climate models
for the periods of 2021-2050 and
2071-2100 with respect to the mean values of 1961-1990

Projection results