# **4.3. The impact of climate change**

Climate change is likely to increase the number of people exposed to floods and droughts. To estimate the range of increase in population exposure, we overlay the drought and flood hazard maps used for this paper with present‐day and projected population density data sets,<sup>7</sup> for a high‐emissions pathway consistent with a 4°C increase in global temperatures. This pathway is known as Representative Concentration Pathway (RCP) 8.5, where global annual GHG emissions (measured in CO2‐equivalents) continue to rise throughout the 21st century. We run the analysis for five Global Circulation Models (GCMs).<sup>8</sup> Across the five models, under a high‐emissions scenario (RCP 8.5), for droughts, we find the number of people exposed could increase by 9–17 percent in 2030 and 50–90 percent in 2080. For floods, the number of people exposed to river floods could increase by 4–15 percent in 2030 and 12– 29 percent in 2080.

To assess how poverty exposure may change in the future as a result of climate change, we calculate the same PEB for a low‐emissions pathway consistent with a 2°C increase (RCP 2.6, where global annual GHG emissions peak between 2010‐2020, and decline substantially thereafter) and RCP 8.5 and for five GCMs. Besides this, we have used the two scenarios to estimate from the household surveys, how much exposure change is to be expected in the future due to climate change. To ensure that we only see the impact of climate on exposure, we do not include compounding effects such as migration and population growth.

The PEB does not change significantly under the two different future climate scenarios and is therefore not displayed. Of course, hazard does not drive exposure and exposure bias alone. The PEB will change in the future due to other driving mechanisms not assessed in this paper, such as migration, changes in the spatial distribution of poverty, or the general increase in income within countries. Countries with rapid urbanization – such as many in Africa – may exhibit major changes in their flood exposure patterns in the coming decades, independently of climate change and other changes in hazards.

Regions where climate change causes an increase in the annual expected number of people exposed to floods and droughts, and where poor people are generally already more exposed than average (i.e. _Ip_ > 0 ) should be treated as highly climate‐sensitive regions for poor people. To locate these, Figure 7 shows the percentage change per country in the annual expected number of people exposed to floods between 1980 and 2050, based on the household data and RCP 8.5, and Figure 8 shows the same for droughts (Table 1 also reproduces results for all countries). RCP 2.6 shows similar changes in exposure although it takes longer before these changes are reached. In some countries, the number of flood‐ exposed people under climate change rises rapidly; this is the case in the Horn of Africa, parts of West Africa, Egypt, Bangladesh, Colombia, and Bolivia. For droughts, the different GCMs employed show more disagreement in drought extremes, causing less significant results. However, if we use the GCM ensemble average we can again see that in particular West African countries show an increase in the number of exposed people.

> 7 For present day, Landscan is used. For 2030 and 2080, data from the Shared Socio‐economic Pathways (SSP4 and SSP5) is used. For more information on the SSPs, see O’Niell et al. 2014.

> 8 A factor delta approach was used to bias correct for the GCM uncertainty. That is, we examined the factor increase between historical GCM runs and future ones (2030,2080) and superimposed this factor increase on top of the EUWATCH results.

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