Climate model and Climate data

Climate model and Climate data

Overview of the climate model and climate data

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This overview includes climate model outputs of annual mean Precipitation, Evaporation, 2-meter Temperature and Precipitation minus Evaporation. These outputs are obtained through numerical simulations performed with the Community Earth System Model (CESM1.2.2) on the North German Supercomputer HLRN3. This is work done bij Sri Nandini, PRIDE early stage researcher from MARUM, Center for Marine Environmental Sciences and Faculty of Geosciences, University of Bremen, Germany.

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Climate model

CESM1.2.2 is a fully coupled global climate model that provides state-of-the-art computer simulations of the Earth’s past, present and future (Hurrell et al., 2013). The coupled simulations employ the Community Atmosphere Model 5 (CAM5) (http://www.cesm.ucar.edu/). The CESM1.2.2 data presented is at ~1° horizontal resolution (1.25° x 0.9°) for the control historical period (1950-2000). The same is done to understand changes in future (2070-2100) compared to present day (1970-2000) under two IPCC scenarios implying different Representative Concentration Pathways (RCP4.5 and RCP8.5) (Lamarque et al., 2011; Meinshausen et al., 2011; Moss et al., 2010; Van Vuuren et al., 2011). 

The RCPs project radiative forcing for different modeled greenhouse gas (GHG) concentration pathways. The RCP8.5 is categorized as high-range scenario with continuously rising GHG emissions throughout the 21st century (Riahi et al., 2007), ending up with a radiative forcing of 8.5 W/m2 by the year 2100.The RCP4.5 is a mid-range scenario where the total radiative forcing is 4.5 W/m2 by the year 2100 and stabilized shortly after (Clark et al., 2007; Smith and Wigley, 2006; Wise et al., 2009). These show how the climate differs in the future for this region under two different GHG emissions.

Climate model data

The diagrams show spatial maps over the Ponto Caspian region for different time periods:


RCP4.5 (2070-2100) minus Historical (1970-2000) to show the rate of change by 2100

2metre temperature:

The surface temperature difference for RCP4.5 (when compared to the historical period)   for the Ponto Caspian region by 2100 shows increased warming by ~3°C generally with the northern Caspian Sea (CS) and western Black Sea (BS) slightly warmer. This is in line with the IPCC projections regarding a future warming world.

Precipitation:

The large-scale precipitation over this region for RCP4.5 (relative to the historical period) shows higher precipitation for the region between the CS and BS [~150 mm/year], south-western region of the CS as well as the over the Volga catchment area; these appear to be wetter by 2100. However, the regions to the south-west of the BS tend to become drier [~80 mm/year], with lower precipitation by 2100.

Evaporation:

Given the higher warming seen in RCP4.5, the CESM evaporation indeed suggests higher evaporation over the western BS and northern and eastern CS [~200-230 mm/year] (perhaps due to the shallow depth (~5-10m) and higher temperatures by 2100; these are relative to the changes seen for historical period. Over the land, evaporation is smallest at south-western BS and eastern CS, denoting the aridity of these sub-regions.

Precipitation minus Evaporation:

The corresponding precipitation minus evaporation (P-E) map for the difference between   RCP4.5 and the historical period shows higher precipitation over land and higher evaporation over the BS and the CS, replication information from the precipitation and evaporation maps seen earlier.


RCP8.5 (2070-2100) minus Historical (1970-2000) to show the rate of change by 2100

2metre temperature:

The surface temperature for RCP8.5 (when compared to the historical period) for the Ponto Caspian region by 2100 is even higher when compared with the RCP4.5 scenario and shows increased warming by ~6°C generally over the land and slightly less over the sea (~4.5°C) with the northern CS and north-western BS slightly warmer. In particular, temperatures on the surface rise to a maximum 7°C poleward over the CS.

Precipitation:

The large-scale precipitation over this region for RCP8.5 (relative to the historical period) shows the sharpest increase in precipitation between the CS and BS [~150 mm/year] and extends further into south-western region of the CS (when compared with the RCP4.5 changes) and less over the Volga catchment area; these appear even wetter by 2100. However, the regions to the south-west of the BS tend to become drier; especially over the Mediterranean region [~80 mm/year], with lower precipitation by 2100. This is also in line with several IPCC and climate modeling literature.

Evaporation

Under the influence of the higher warming seen in RCP8.5 (compared with the historical as well as the RCP4.5), the CESM evaporation suggests even higher evaporation over the western BS and northern and eastern CS [~250-300 mm/year] by 2100. Over the land, evaporation is smallest at south-western BS and eastern CS, denoting the aridity of these sub-regions. The Mediterranean region also shows enhanced evaporation under the RCP8.5 by 2100.

Precipitation minus Evaporation

The precipitation minus evaporation (P-E) map for the difference between   RCP8.5 and the historical period shows even more enhanced precipitation over land and higher evaporation over the BS and the CS, replication information from the precipitation and evaporation maps seen earlier; and also, higher then what is seen for the RCP4.5.

In generally, the CESM model projections suggest climate change in the Ponto-Caspian region is not uniform, with some sub regions undergoing higher warming, enhanced evaporation and precipitation, while other sub regions will show opposing effects. As expected and in line with several IPCC modeling projections, the RCP8.5 brings a world of higher warming, evaporation and variable precipitation changes which are influenced by extreme and large-scale seasonal climate changes as well.

Importance of Climate data for the Caspian Region

The Caspian Sea level (CSL) has undergone dramatic variations of more than 3 m during the past century with important implications for the life of coastal people, economy and the ecosystem. The origin of these variations as well as future changes in the Caspian water budget are still a matter of debate.  The generated climate data are the only tool for adapting or better preparing for the future impacts of climate change (e.g. severe drought/flood) caused by fluctuations in precipitation minus evaporation in this region. However, modelled data should be treated with caution as they include uncertainties and biases as well and are not the absolute truth on future changing climate. Hence the modeled data maps shown here may be used as a cautionary inclusion in designing a protocol towards mitigation and resilience from changes in the future CSL.

Overall, for more information on these climate model outputs regarding this region, the reader is welcomed to contact Sri Nandini1 (snandini@marum.de).