Indicators of climate risk in the UK at different levels of warming

Abstract

Assessments of the impacts of climate change are typically made using climate scenarios based on assumptions about future emissions of greenhouse gases, but policymakers and climate risk communicators are increasingly asking for information on impacts at different levels of warming. This paper provides this information for a set of indicators of climate risks in the UK for levels of warming up to 4 °C above pre-industrial levels. The results show substantial increases in climate risks at 2 °C, which is often inferred in the media to be a ‘safe’ level of climate change. In a 2 °C world, the chance of a heatwave is doubled, and the frequency of heat stress affecting people, crops and animals can be increased by a factor of five. Cooling degree days more than double, wildfire danger can increase by 40%–70%, the frequency of agricultural and water resources droughts doubles in England, and flood frequency in Wales increases by 50%. At 4 °C the increases in risk are considerably greater: heatwaves occur in virtually every year. The frequency of cold weather extremes reduces, but is not eliminated, with increasing warming. The rate of change in an indicator with warming varies across the UK. For temperature-based indicators this reflects variability in current climate, but for rainfall-based indicators reflects variations in the change in climate. Most indicators show a generally linear increase in risk with level of warming (although the change in risk from now is around 2.4 times higher in a 4 °C world than a 2 °C world because of warming experienced so far). However, some indicators—particularly relating to heat extremes—show a highly non-linear increase with level of warming. The range in change in indicator at a given level of warming is primarily caused by uncertainty in the estimated regional response of to increasing forcing.

Climate Change, Grape Phenology, and Frost Risk in Southeast England

“…Tis may indicate that climate variability at interannual to decadal timescales will continue to be a feature of the Southeast England viticulture region. Tis assertion is supported by the results from recent climate projections for England, which show that while the frequency of cold weather extremes may reduce under climate change, their elimination is not total, even under a global warming of 4 °C [52].…”

“…Increased heat may therefore pose a threat to grape health [56,57], with the prospect that some wine regions may become unsuitable for viticulture in the future due to heat extremes [7]. Tis is important in the context of the wider Southeast England region, as although the average climate may become more conducive to wine production and agriculture in general, heatwaves will double in frequency, with the likelihood of heat stress afecting crops projected to increase by a factor of fve with a global warming of 2 °C, as pointed out by Arnell et al [52].…”

Updated projections of UK heat-related mortality using policy-relevant global warming levels and socio-economic scenarios

“…For each global warming level, daily TMean data for each 30 year period, representative of the different levels of global warming above pre-industrial temperatures, were extracted. The 30 year time periods for each global warming level were based on start and end years published in Arnell et al [33], with the exact years for each global warming level varying slightly between UKCP18 RCM simulations. We note that this approach approximates each global warming level, and that the true climate at an equilibrated global warming level will be different from the transient global warming level presented here.…”

Climate change impacts on flood peaks in Britain for a range of global mean surface temperature changes

“…Others have used scenarios representing specific temperature targets constructed by ‘time‐sampling’ (James et al, 2017) periods from a climate model simulation with the desired mean change in global temperature to estimate impacts on droughts (Naumann et al, 2018), extreme weather events and water availability (Schleussner et al, 2016), and crop yields (Ostberg et al, 2018). Arnell et al (2021) demonstrate the sensitivity of climate risks in the United Kingdom to level of warming, and highlight the considerable regional variability in impact for some indicators, including flooding. This study used the response surfaces of Kay et al (2021), onto which ‘time‐sampled’ probabilistic projections were overlain to extract flood peak changes.…”

“…By providing flood peak changes relative to levels of GMST change, rather than by future time‐slice and emission scenario as done previously, the results directly illustrate the additional impact that higher levels of GMST change could have, regardless of the future time‐period in which the level is reached or what emissions trajectory is followed. This helps to address the increasing demand from policymakers for evidence on the potential impacts of specific levels of change in GMST (Arnell et al, 2019, 2021). Other studies have presented large‐scale global and regional impacts of climate change on floods for specific GMST changes, but this study goes further by providing 1 km‐scale impact projections for GB.…”