**2. Previous studies of migration and climate change**

Climate-oriented scientists agree that the likely harmful effects of climate change on rural economies have grown stronger over time. According to [12], almost 870 million globally are chronically undernourished amid climate models predicting rising temperature and declining precipitation for most of Sub-Saharan Africa [6, 12]. Many sub-Saharan economies dominantly depend on climate-sensitive agricultural production, and this region's people are already facing starvation with more than 60% living below the poverty line [13].

According to the Intergovernmental Panel on Climate Change, about 150–200 million people will likely be displaced globally by 2050 due to anthropogenic climate changes [14]. Consensus among global scholars suggests climate change induced migration will worsen in the future [15]. Warming temperatures will have severe effects over the interior semi-arid margins of the Sahara and central southern Africa [1]. Similarly, Africa has remained hot and dry, but is warmer than it was 100 years ago [16–18].

Sub-Saharan Africa precipitation patterns are highly influenced by inter-seasonal and inter-annual climate variability including occasional El Niño-Southern Oscillation events [19–21]. Eastern equatorial Africa is heavily affected by extreme meteorology during the short October–November rainy season, while southeastern Africa experiences similar conditions during the main rainy season in November–February [22–24]. Hulme et al. [16] illustrates the nature of rainfall variability for the Sahel, East Africa, and southeastern regions, and suggests these three regions show contrasting variability. The Sahel shows large multi-decadal variability with recent drying, while east Africa demonstrates a relatively steady regime with some evidence of long-term wetting. By contrast southeast Africa tends to exhibit stability, with some noticeable inter-decadal variation [22], indicating higher latitudes are more susceptible to climate forcings.

#### *Spatial Analysis of Climate Driver Impacts on Sub-Saharan African Migration Patterns… DOI: http://dx.doi.org/10.5772/intechopen.106067*

Tanzanian climate projections show an expected mean annual temperature increase of 1.7–2.5°C by the 2060s, suggesting a stronger increase than the global average [25]. Similarly, mean annual rainfall patterns are also projected to increase across the country, but with a complex seasonal pattern highlighted by increased January and February rainfall, most dramatically in the far south. For northern Tanzania, highest rainfalls are expected for March, April, and May. During June, July, August, and September, precipitation is projected to increase in the very north of the country, while central and southern Tanzania expect declining rainfall [26].

Migration is a key rural livelihood strategy to increase household earning potential [27], reduce income risk, and shield against socioeconomic and environmental shocks [28]. Migration is a family response to income risk where migrants serve as an income insurance policy for their households of origin [28]. Households effectively diversify income sources by allocating labor to areas with a different set of risks from those faced in the source region, thereby building resilience to various livelihood shocks [29].

In their study on Ecuador, [30] show agricultural shocks are key factors in international migration. Munshi et al. [31, 32] have shown strong links between climate change, crop yields, and migration, whereas [33] discovered an opposite relationship suggesting Mexico to U.S. migration decreases as rainfall declines. Ethiopian studies show rural out-migration responds to drought sensitivity [34, 35].

There seems to be lack of consensus on the role of disasters in international migration with some arguing for a positive link [36–39], while others indicate little or no or a negative relationship [40, 41]. For instance, [40] found flooding has modest to insignificant impacts on migration. On the other hand, [41] discovered people did not migrate after the occurrence of disaster in Bangladesh.

Meze-Hausken [35] showed weather anomaly impact on international migration has two channels. First, weather anomalies will lead to lower rural wages, especially if the effect of weather anomalies on agricultural production is strong. Second, lower rural wages will attract more mobile workers to move from the rural areas to cities in search of work. Consequently, more people settle in urban areas and thus increase urbanization. Therefore, weather anomalies are a key determinant of increased urbanization.

The growing literature examining the migration determinants increasingly emphasizes the role of environmental change in in-migration processes. Nawrotzkia and Maryia [42] show there are different ways to measure climatic factors. Heat waves, cold snaps, droughts, and excessive precipitation can be thresholds to construct climate measures. Schlenker and Roberts [43] investigated temperature effects on corn, soybeans, and cotton based on nationwide crop yield data and growing season climate information. Their findings indicate threshold temperatures for each crop with temperatures above the respective thresholds leading to yield reductions.

The literature therefore suggests strong links between climate change and migration. Climate change and migration relationships are relatively well researched from a non-spatial perspective. Spatially explicit empirical research in this context is in its infancy, especially for regions like Africa. Therefore, the present study seeks to address the paucity of empirical studies in the region. Another important knowledge gap is the literature's focus on precipitation or temperature variation, while neglecting the effect they may have jointly on migrant decisions. Therefore, a clear understanding of climate change impacts on migration requires assessment of spatial links between climate change and migration. Further, impacts of temperature and precipitation variations on individual and household migration decisions need to be assessed in the same framework.
