The risk of extreme climatic conditions leading to unusually low global agricultural production is exacerbated if more than one global 'breadbasket' is subject to climatic extremes at the same time. Such shocks can pose a risk to the global food system amplifying threats to global food security 1,2 and have the potential to trigger other systemic risks 3,4. So far, while the possibility of climatic extremes hitting more than one breadbasket has been postulated 5,6 little is known about the actual risk. Here we present quantitative risk estimates of simultaneous breadbasket failures due to climatic extremes and show how risk has changed over time. We combine region-specific data on agricultural production with spatial statistics of climatic extremes to quantify the changing risk of low production for the major food producing regions ('breadbaskets') in the world. We find evidence that there is increasing risk of simultaneous failure of wheat, maize and soybean crops, across the breadbaskets analyzed. For rice, risks of simultaneous adverse climate conditions have decreased in the breadbaskets analyzed in this study in the recent past mostly owing to solar radiation changes favoring rice growth. Depending on the correlation structure between the breadbaskets, spatial dependence between climatic extremes globally can mitigate or aggravate the risks for the global food production. Our analysis can provide the basis for more efficient allocation of resources to contingency plans and/or strategic crop reserves that would enhance the resilience of the global food system. Climate variability explains at least 30% of year-to-year fluctuations in agricultural yield 7. Under 'normal' climatic circumstances the global food system can compensate local crop losses through grain storage and trade 8. However, it is doubtful whether the global food system is resilient to more extreme climatic conditions 9 , when export restrictions 10 and diminished grain stocks may undermine liquidity in agricultural commodity markets, resulting in higher price volatility. The food price crisis in 2007/08 has shown that climatic shocks to agricultural production contribute to food price spikes 1 and famine 2 , with the potential to trigger other systemic risks including political unrest 3 and migration 4. Climatic teleconnections between global phenomena such as El Niño Southern Oscillation (ENSO) and regional climate extremes such as Indian heatwaves 11 or flood risks around the globe 12 could lead to simultaneous crop failure in different regions, therefore posing a risk to the global food system 8,10 , and amplifying threats to global food security. While the possibility of a climatic extreme hitting more than one breadbasket has been a growing cause for concern 5,6 , only few studies have investigated the probability of simultaneous production shocks 13 or estimated the joint likelihoods of adverse climate conditions 14. Here we present, to our knowledge for the first time, quantitative risk estimates of simultaneous breadbasket failures due...

The increasingly interconnected global food system is becoming more vulnerable to production shocks owing to increasing global mean temperatures and more frequent climate extremes. Little is known, however, about the actual risks of multiple breadbasket failure due to extreme weather events. Motivated by the Paris Climate Agreement, this paper quantifies spatial risks to global agriculture in 1.5 and 2°C warmer worlds. This paper focuses on climate risks posed to three major crops-wheat, soybean and maize-in five major global food producing areas. Climate data from the atmosphere-only HadAM3P model as part of the "Half a degree Additional warming, Prognosis and Projected Impacts" (HAPPI) experiment are used to analyse the risks of climatic extreme events. Using the copula methodology, the risks of simultaneous crop failure in multiple breadbaskets are investigated. Projected losses do not scale linearly with global warming increases between 1.5 and 2°C Global Mean Temperature (GMT). In general, whilst the differences in yield at 1.5 versus 2°C are significant they are not as large as the difference between 1.5°C and the historical baseline which corresponds to 0.85°C above pre-industrial GMT. Risks of simultaneous crop failure, however, do increase disproportionately between 1.5 and 2°C, so surpassing the 1.5°C threshold will represent a threat to global food security. For maize, risks of multiple breadbasket failures increase the most, from 6% to 40% at 1.5 to 54% at 2°C warming. In relative terms, the highest simultaneous climate risk increase between the two warming scenarios was found for wheat (40%), followed by maize (35%) and soybean (23%). Looking at the impacts on agricultural production, we show that limiting global warming to 1.5°C would avoid production losses of up to 2 753 million (161 000, 265 000) tonnes maize (wheat, soybean) in the global breadbaskets and would reduce the risk of simultaneous crop failure by 26%, 28% and 19% respectively.

Societies and economies are challenged by variable water supplies. Water storage infrastructure, on a range of scales, can help to mitigate hydrological variability. This study uses a water balance model to investigate how storage capacity can improve water security in the world's 403 most important river basins, by substituting water from wet months to dry months. We construct a new water balance model for 676 'basin-country units' (BCUs), which simulates runoff, water use (from surface and groundwater), evaporation and trans-boundary discharges. When hydrological variability and net withdrawals are taken into account, along with existing storage capacity, we find risks of water shortages in the Indian subcontinent, Northern China, Spain, the West of the US, Australia and several basins in Africa. Dividing basins into BCUs enabled assessment of upstream dependency in transboundary rivers. Including Environmental Water Requirements into the model, we find that in many basins in India, Northern China, South Africa, the US West Coast, the East of Brazil, Spain and in the Murray basin in Australia human water demand leads to over-abstraction of water resources important to the ecosystem. Then, a Sequent Peak Analysis is conducted to estimate how much storage would be needed to satisfy human water demand whilst not jeopardizing environmental flows. The results are consistent with the water balance model in that basins in India, Northern China, Western Australia, Spain, the US West Coast and several basins in Africa would need more storage to mitigate water supply variability and to meet water demand.