Editing IPCC:AR6/WGII/Chapter-5 (section)

=== 5.11.3 Current and Projected Impacts on Transportation and Distribution: Domestic and International Trade ===

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Regional differences in resource availability are a key underlying driver of domestic and international trade. Climate change can change resource availability, in terms of both quantity and quality, altering trade flows, prices and incomes of producers. Climate change can also affect food access, and its stability can be affected through climate-change-driven disruption of infrastructure ( [[#FAO--2018|FAO et al., 2018]] ; [[#Mbow--2019|Mbow et al., 2019]] ). Extreme events are expected to become more common as climate change progresses. Recent examples illustrate the potential for trade disruptions. In March 2019, Cyclone Idai affected 1.7 million people in Mozambique and 920,000 in neighbouring Malawi, according to United Nations (UN) officials. The World Food Program reported that satellite imagery of flooding in central Mozambique showed an ‘inland ocean’ the size of Luxembourg with potentially large impacts on distribution of existing supplies, and uncertain effects on future food production and availability. The extreme rainfall events in the US state of Iowa in spring 2019 destroyed large numbers of well-built grain silos. In addition, major road and bridge damage required rebuilding.

Trade plays a sizeable role in global food supplies. More than 1 billion people relied on international food trade in the early 21st century ( [[#Fader--2013|Fader et al., 2013]] ; Pradhan, 2014). Domestic and international trade flows can be dramatically affected by climate change impacts ''(medium evidence'' , ''high confidence)'' ( [[#Nelson--2014|Nelson et al., 2014]] ; Pradhan, 2014; [[#Wiebe--2015|Wiebe et al., 2015]] ) ''.'' Since the impacts of climate change will not be uniform, profitable locations for exports production will change. In addition, the effects of increasing local weather variability caused by climate change means increasing variability of food availability for domestic use and international trade. Finally, extreme events driven by climate change can disrupt transportation along the food value chain. Countries more at risk of natural hazards that disrupt transportation and distribution, and with less extensive routes, are more vulnerable to climate change impacts. A global multi-hazard risk assessment ( [[#Koks--2019|Koks et al., 2019]] ) suggests surface and river flooding, which are projected to increase in a warmer climate, are the main hazards for road and railway infrastructure, increasingly disrupting international and domestic transportation of agricultural commodities.

Climate change impacts will increase most global prices relative to early 21st century levels, with varying effects on the cost of food imports ( ''high confidence'' ) ( [[#Nelson--2014|Nelson et al., 2014]] ; [[#Wiebe--2015|Wiebe et al., 2015]] ; [[#Fujimori--2018|Fujimori et al., 2018]] ; [[#Lee--2018|Lee et al., 2018]] ). For example, analysis using results from one study (using CMIP5 data for RCP8.5 and SSP2) found that net food importing countries in the early 21st century would see expenditures on food imports decrease by USD 36 billion in mid-century in real terms with climate change over a no climate change scenario. (Table 5.13).

'''Table 5.13 |''' Net exports of agricultural products, by net exporting and net importing countries, 2010 and 2050 (billion constant parity US dollars), based on analysis in [[#Beach--2019|Beach et al. (2019)]] .

{| class="wikitable"
|-
!
! 2010

! 2050

|-
| Net importers in 2010

|
|-
| No climate change

| –301

| −838

|-
| Climate change

| −301

| −802

|}

Global economic models with a focus on agriculture provide a perspective on the range of potential changes in market outcomes because of climate change. In one study comparing several SSPs to a future with no climate change to one with impacts from RCP8.5, 2050 yields with climate changes impacts are 17% smaller on average than those without climate change. Adaptation by farmers reduce that to an 11% decline. The change in 2050 prices of all crops and regions after climate change impacts and farm-level adaptation is a mean 20% increase ( [[#Nelson--2014|Nelson et al., 2014]] ). Substantial differences arise from both the heterogeneous impacts of climate change over crops and geography and the diversity of modelling approaches in the GCM and crop models. A later study with more socioeconomic scenarios and fewer models got roughly similar results ( [[#Wiebe--2015|Wiebe et al., 2015]] ), as did a modelling study focused on food security in South Asian countries ( [[#Cai--2016|Cai et al., 2016]] ).

Most climate scenario modelling to date does not incorporate increasing variability nor the use of storage, a critical tool to manage variability. Two recent studies are exceptions. In one, climate change generally reduces mean yields and increases their variability in the Midwestern USA and causes modest increases in price volatility ( [[#Thompson--2018|Thompson et al., 2018]] ). A second study ( [[#Chen--2019|Chen and Villoria, 2019]] ) focuses on maize net importers across Africa, Asia and Latin America during 2000–2015. A 1% increase in the ratio of imports to total consumption reduces domestic price variability by 0.29%. A 1% increase in stocks at the beginning of the season is correlated with a 0.22% reduction in the coefficient of variation.

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