Part of the Middle East and North Africa may become uninhabitable due to climate change driven extreme heat, say researchers, prompting fears of a climate-exodus from the region.
From the Max Planck Institute for Chemistry
The number of climate refugees could increase dramatically in future. Researchers of the Max Planck Institute for Chemistry and the Cyprus Institute in Nicosia have calculated that the Middle East and North Africa could become so hot that human habitability is compromised. The goal of limiting global warming to less than two degrees Celsius, agreed at the recent UN climate summit in Paris, will not be sufficient to prevent this scenario. The temperature during summer in the already very hot Middle East and North Africa will increase more than two times faster compared to the average global warming. This means that during hot days temperatures south of the Mediterranean will reach around 46 degrees Celsius (approximately 114 degrees Fahrenheit) by mid-century. Such extremely hot days will occur five times more often than was the case at the turn of the millennium. In combination with increasing air pollution by windblown desert dust, the environmental conditions could become intolerable and may force people to migrate.
More than 500 million people live in the Middle East and North Africa – a region which is very hot in summer and where climate change is already evident. The number of extremely hot days has doubled since 1970. “In future, the climate in large parts of the Middle East and North Africa could change in such a manner that the very existence of its inhabitants is in jeopardy,” says Jos Lelieveld, Director at the Max Planck Institute for Chemistry and Professor at the Cyprus Institute.
Lelieveld and his colleagues have investigated how temperatures will develop in the Middle East and North Africa over the course of the 21st century. The result is deeply alarming: Even if Earth’s temperature were to increase on average only by two degrees Celsius compared to pre-industrial times, the temperature in summer in these regions will increase more than twofold. By mid-century, during the warmest periods, temperatures will not fall below 30 degrees at night, and during daytime they could rise to 46 degrees Celsius (approximately 114 degrees Fahrenheit). By the end of the century, midday temperatures on hot days could even climb to 50 degrees Celsius (approximately 122 degrees Fahrenheit). Another finding: Heat waves could occur ten times more often than they do now.
In addition, the duration of heat waves in North Africa and the Middle East will prolong dramatically. Between 1986 and 2005, it was very hot for an average period of about 16 days, by mid-century it will be unusually hot for 80 days per year. At the end of the century, up to 118 days could be unusually hot, even if greenhouse gas emissions decline again after 2040. “If mankind continues to release carbon dioxide as it does now, people living in the Middle East and North Africa will have to expect about 200 unusually hot days, according to the model projections,” says Panos Hadjinicolaou, Associate Professor at the Cyprus Institute and climate change expert.
Atmospheric researcher Jos Lelieveld is convinced that climate change will have a major impact on the environment and the health of people in these regions. “Climate change will significantly worsen the living conditions in the Middle East and in North Africa. Prolonged heat waves and desert dust storms can render some regions uninhabitable, which will surely contribute to the pressure to migrate,” says Jos Lelieveld.
The research team recently also published findings on the increase of fine particulate air pollution in the Middle East. It was found that desert dust in the atmosphere over Saudi Arabia, Iraq and in Syria has increased by up to 70 percent since the beginning of this century. This is mainly attributable to an increase of sand storms as a result of prolonged droughts. It is expected that climate change will contribute to further increases, which will worsen environmental conditions in the area.
In the now published study, Lelieveld and his colleagues first compared climate data from 1986 to 2005 with predictions from 26 climate models over the same time period. It was shown that the measurement data and model predictions corresponded extremely well, which is why the scientists used these models to project climate conditions for the period from 2046 to 2065 and the period from 2081 to 2100.
Largest temperature increase in already hot summers
The researchers based their calculations on two future scenarios: The first scenario, called RCP4.5, assumes that the global emissions of greenhouse gases will start decreasing by 2040 and that the Earth will be subjected to warming by 4.5 Watt per square meter by the end of the century. The RCP4.5 scenario roughly corresponds to the target set at the most recent UN climate summit, which means that global warming should be limited to less than two degrees Celsius.
The second scenario (RCP8.5) is based on the assumption that greenhouse gases will continue to increase without further limitations. It is therefore called the “business-as-usual scenario”. According to this scenario, the mean surface temperature of the Earth will increase by more than four degrees Celsius compared to pre-industrial times.
In both scenarios, the strongest rise in temperature in the Middle East and North Africa is expected during summer, when it is already very hot, and not during winter, which is more common in other parts of the globe. This is primarily attributed to a desert warming amplification in regions such as the Sahara. Deserts do not buffer heat well, which means that the hot and dry surface cannot cool by the evaporation of ground water. Since the surface energy balance is controlled by heat radiation, the greenhouse effect by gases such as carbon dioxide and water vapor will increase disproportionately.
Regardless of which climate change scenario will become reality: both Lelieveld and Hadjinicolaou agree that climate change can result in a significant deterioration of living conditions for people living in North Africa and the Middle East, and consequently, sooner or later, many people may have to leave the region.
Strongly increasing heat extremes in the Middle East and North Africa (MENA) in the 21st century
The ensemble results of CMIP5 climate models that applied the RCP4.5 and RCP8.5 scenarios have been used to investigate climate change and temperature extremes in the Middle East and North Africa (MENA). Uncertainty evaluation of climate projections indicates good model agreement for temperature but much less for precipitation. Results imply that climate warming in the MENA is strongest in summer while elsewhere it is typically stronger in winter. The summertime warming extends the thermal low at the surface from South Asia across the Middle East over North Africa, as the hot desert climate intensifies and becomes more extreme. Observations and model calculations of the recent past consistently show increasing heat extremes, which are projected to accelerate in future. The number of warm days and nights may increase sharply. On average in the MENA, the maximum temperature during the hottest days in the recent past was about 43 °C, which could increase to about 46 °C by the middle of the century and reach almost 50 °C by the end of the century, the latter according to the RCP8.5 (business-as-usual) scenario. This will have important consequences for human health and society.
Aerosol optical depth trend over the Middle East
We use the combined Dark Target/Deep Blue aerosol optical depth (AOD) satellite product of the moderate-resolution imaging spectroradiometer (MODIS) collection 6 to study trends over the Middle East between 2000 and 2015. Our analysis corroborates a previously identified positive AOD trend over large parts of the Middle East during the period 2001 to 2012.
We relate the annual AOD to precipitation, soil moisture and surface winds to identify regions where these attributes are directly related to the AOD over Saudi Arabia, Iraq and Iran. Regarding precipitation and soil moisture, a relatively small area in and surrounding Iraq turns out to be of prime importance for the AOD over these countries. Regarding surface wind speed, the African Red Sea coastal area is relevant for the Saudi Arabian AOD.
Using multiple linear regression we show that AOD trends and interannual variability can be attributed to soil moisture, precipitation and surface winds, being the main factors controlling the dust cycle. Our results confirm the dust driven AOD trends and variability, supported by a decreasing MODIS-derived Ångström exponent and a decreasing AERONET-derived fine mode fraction that accompany the AOD increase over Saudi Arabia. The positive AOD trend relates to a negative soil moisture trend. As a lower soil moisture translates into enhanced dust emissions, it is not needed to assume growing anthropogenic aerosol and aerosol precursor emissions to explain the observations. Instead, our results suggest that increasing temperature and decreasing relative humidity in the last decade have promoted soil drying, leading to increased dust emissions and AOD; consequently an AOD increase is expected due to climate change.
Max Planck Institute for Chemistry news release.