The water crisis at the centre of the new IPCC report

This report is the result of work by 270 authors from 67 countries who have synthesised and coordinated more than 34,000 scientific articles.

The general observation is gloomy: the average temperature of the world has already risen by 1.09°C in comparison to the pre-industrial era (reference period: 1850-1900). In addition to the irreversible damage already done due to global warming caused by human beings, the extent and magnitude of the impacts analysed are particularly severe when compared to other publications of the intergovernmental panel. The panel considers that most of the risks mentioned (droughts, heatwaves, storms) are inevitable, although specific and speedy adaptation measures could mitigate their impact on populations.

The issue of water is crucial for adapting to climate change

 

Although the issue of water is considered crucial throughout the report, Chapter 4 is devoted specifically to the impact of climate change on hydrological cycles. The authors emphasise that extreme climatic events such as floods and droughts have become probable and are more severe due climate change of human origin. However, drought and flood episodes have not waited to increase in frequency and intensity: since the 1970s, 44% of climatic disasters have been linked to floods, and it is estimated that today already, half of humanity suffers from water shortages at least one month every year.

Regarding future changes, it is estimated that between 42% and 79% of the world’s hydrographic basins will be critically affected from now to 2050, which will have a considerable impact on freshwater ecosystems and the capacity of reservoirs to ensure secure water supplies. Moreover, the share of the population subject to extreme drought will rise from 3% to 8% by 2100. Regarding the cause of these disturbances, the authors repeat that they are above all due to anthropogenic climate change, before being the consequence of direct human activities on these resources (mainly land-use and water management).

The authors also underline that these exceptional modifications of hydrological cycles follow a dual trend. Whereas the impact of climate change will lead to the reduction of average discharges in North America and the East, South Europe, Northeast Asia and the Indian subcontinent, it will probably lead to an increase of discharges in North Europe. Furthermore, if the global increase of temperatures reaches 4°C, it is estimated that 10% of the world’s land surface will undergo extremely high and low discharges simultaneously from now to 2100, affecting the daily lives of 2.1 billion people.

 

Every degree counts in the combat against climate change

 

The report underlines that the efficiency of adaptation to these hydrological disturbances greatly depends on the warming scenario considered. To adapt to risks relating to water (drought, floods, heatwaves), the report emphasises the efficiency of measures decreases considerably for an increase in temperature of 2°C, making it even more necessary to remain below the warming threshold of +1.5°C. But even if this scenario is realised, adaptive capacities remain limited, notably for islands and regions dependent on glaciers and snow melt.

The issue of social justice at the heart of the report

 

Obviously, the report insists on the fact that the impacts of climate change, for the most part negative, are felt disproportionately by already vulnerable populations. Changes in hydrological cycles will first affect “the poor, women, children, indigenous communities and the elderly everywhere in the world and in particular in the Southern hemisphere, due to the systemic inequalities bequeathed by a historic process of socioeconomic and political marginalisation”, says the panel.

In addition, countries with low incomes are confronted by other barriers when trying to obtain funds for adaptation projects, given the pressures already burdening their budgets. Furthermore, in the case of water resources, adaptive measures can come into conflict with climate change mitigation measures, and thus lead to difficult trade-offs. The report underlines that carbon sequestration biomass, reforestation and planting projects require considerable quantities of water, which could threaten the security of water supplies for different populations.

Linked to the issue of environmental justice, the report deals with the issue of climatic migrations, and insists on the unfair nature of these movements of populations. The panel estimates that the hydrological changes caused by climate change will increase by seven-fold the number of demands for asylum in the European Union, and five-fold the internal migrations of populations in regions south of the Sahara, and in South Asia and South America.

The considerable contribution of the social and economic sciences 

 

The impacts of climate change are also assessed in monetary terms, which is a substantial difference from the panel’s first report. In Chapter 4, the experts observe that changes in the hydrological cycle due to climate change between 1983 and 2009 have caused losses to agriculture amounting to $166 billion. The risks and impacts are also assessed in terms of past and future losses of GDP. Losses linked to water could reduce GDP by 0.1% to 0.49%, with an increase in this figure for poor and developing countries.

The report also highlights other types of knowledge, by acknowledging the importance of “local, indigenous and technical” knowhow. In order to avoid implementing poorly adapted policies that block situations of vulnerability and exposure to risks, adaptation policies must result from cooperation between these different types of knowhow.