If we think about actually dangerous issues, it might have an effect on crop yields. • Are you completed with that?
Gotta love this study:
emphasis mine. Oh, and it’s all RCP 8.5 tied into their imagineering engine.
Previous analyzes of the possibility of global granary failures have extrapolated risks based on historical relationships between climate and yields. However, climate change causing unprecedented events worldwidewhich could exceed the critical thresholdS and reduce yields, although there is no historical precedent for doing so. It means that We probably underestimate the climate risks to our food system. In the case of wheat, there is little historical relationship between yields and temperature in parts of the US and China, but extreme temperatures exceeding critical physiological thresholds in wheat plants are now possible. UNSEEN (Unprecedented Simulated Extreme ENsemble) approaches use large ensembles to generate plausible, unprecedented events that may influence our assessment of risk to crops. We use the UNSEEN approach with a large ensemble of archived seasonal forecasts to generate thousands of plausible events over the past 40 years and compare the results to historically observed extreme temperatures and precipitation. In the US Midwest, extreme temperatures that occurred about once every 100 years in 1981 are now recurring every sixth year, while in China the current return period is on the order of one -16 years. This means that in the US Midwest, extreme temperatures that had a 1% chance of occurring in 1981 now have a 17% chance of occurring each year, while in China the chance has increased from 1% to 6%. Record years in which critical thresholds for enzymes in the wheat plant are exceeded are more likely today than in the past, and these record-breaking hot years are associated with extremely dry conditions at both locations. Using geopotential height and wind anomalies from the UNSEEN ensemble, we show that strong overland winds pull dry air into these regions during extremely hot and dry unseen events. We characterize plausible extremes from the UNSEEN ensemble that can be used to envision otherwise unforeseen events, including a compound event where strong impacts occur simultaneously in both regions and affect adaptation planning in those regions. Recent temperature extremes, particularly in the US Midwest, are probably not a good indicator of what to expect with today’s climate for years to come, and local stakeholders may underestimate their risk as lower than it actually is. We find that there is a high potential for surprise in these regions when risk analyzes are based solely on historical datasets.
Given the global interconnectedness of the world food system, simultaneous shocks in key grain producing areas (granaries) can dramatically affect the price and availability of staple foods. Several studies have attempted to quantify the risk of multiple granary failures due to climate shock alone1,2,3. These studies have primarily extrapolated from historical patterns and quantified the risk that past climate shocks could occur simultaneously in the future. However, climate change brings with it new and unprecedented events that may have different outcomes than those we have experienced in the past, and history-based analyzes may therefore underestimate our current risk. In this study, we no longer focus on historical events, instead showing how to visualize the risk of historically unprecedented events that could breach critical thresholds in key wheat-growing regions of the US and China.
Most studies quantifying the risk of crop failure use historical relationships between climate and crop yields as a basis for estimating how future or unprecedented climate states might affect yields. For example,2 uses historical yields to define a threshold for severe water stress in corn-growing regions of the US and China, and then examines the change in risk of that threshold using large ensembles to simulate unprecedented extremes. Estimates of the risk of multiple granary failures for different crops also follow this approach. It first estimates climate-yield relationships using historical data, and then extrapolates yield results based on changes in temperature and precipitation variables historically associated with yield.4 In some regions, more than 50% of historical yield variations are attributed to the weather5.
However, in a changing climate, the climate-yield relationships will change. Never-before-seen climatic states and unprecedented events can have greater impacts on crops than might be expected from a simple extrapolation of historical context. With regard to temperature in particular, it is to be expected that unprecedented high temperatures could lead to crop failures, even if there is no historical relationship between yield and temperature. Nonlinear responses of crops to heat stress can make the future look significantly different than the past. In addition, climatic stressors combined with other pressures can threaten agricultural productivity. Examples include conflict, pests, disease, soil health, seed quality and irrigation.
Wheat (Triticum aestivum L.) yields in parts of the United States and China do not show a strong association with temperature in historical observed or simulated data sets6, and thus extreme temperatures in these regions are not often included in models for potential granary failures4 . However, physiological models show that wheat plants are temperature sensitive at several critical growth stages7. In general, prolonged periods of extreme heat lead to accelerated leaf aging and a reduction in leaf elongation and radiation use efficiency. Short-term heat events are particularly damaging during sensitive development phases such as stem elongation. Heat extremes during grain filling can lead to reductions in growth rate and grain count8,9, while heat stress during flowering can result in partial or full floret sterility10,11.
End-of-century simulations show that unprecedented temperatures are likely to impact yields as higher thresholds are crossed12 Indeed, process-based and statistical models tend to agree that warming should adversely affect wheat yields13,8 and a review of different model types found agreement that global wheat yields are likely to be adversely affected by rising temperatures associated with climate change14,15. One solution to assessing the impact of this non-linearity is to use crop model simulations, which can incorporate critical thresholds.16,17 However, many of these crop models are developed based on historical yields, and many of them focus on annual extremes and “likely” ranges . rather than low probability, high impact events.
New methods of simulating unprecedented extremes can expand our understanding of what is possible beyond historical events. Large ensembles of physics-based climate models can provide a larger sample of “alternative realities” for calculating extreme value statistics18,19,20 An example is the UNSEEN (UNPrecedented Simulated Extremes using ENsembles) approach, which uses large ensembles of archived forecasts for better understanding Extreme21.
To date, most studies of UNVISIBLE events or climate histories assume an extreme historical event that has already occurred and assess plausible changes in frequency and magnitude (e.g. Storm Desmond22). The approach was also used to derive analogies to future effects of historical events, such as a soybean (Glycine max (L.) Merr.) drought in the future17.
The UNSEEN approach can also be used to explore synthetic events – events with no historical analogue – if the models have been properly validated for their ability to produce realistic events23. Climate stories that illustrate how record-breaking extremes can occur can stretch our imaginations to capture events that are plausible but have never been experienced before. Given that climate change adaptation is typically triggered by people’s lived experience of extreme events,24,25,26,27 visualizing such events before they occur can support climate change preparedness and adaptation.
In this study, we use the UNSEEN approach to examine storylines of unprecedented heat in two wheat-producing regions of the world’s breadbaskets, the US and China. First, we assemble a large ensemble of archived temperature and precipitation forecasts for each region and estimate the frequency of temperatures above critical growth thresholds. We estimate changes in extreme temperature return periods with climate change, accounting for the likelihood of a composite extreme of high temperature and low precipitation in each region. While many other studies have focused on climate change in the distant future, we examine current climate and how risks have already changed from the recent past and complement the work1.
Read the rest of this “paper” here.