Volume 9 Issue 12, December 2019

Minimizing the adverse consequences of sea-level change presents a key societal challenge. New modelling is necessary to examine the implications of global policy decisions that determine future greenhouse gas emissions and local policies around coastal risk that influence where and how we live.

Misleading claims about mass migration induced by climate change continue to surface in both academia and policy. This requires a new research agenda on ‘climate mobilities’ that moves beyond simplistic assumptions and more accurately advances knowledge of the nexus between human mobility and climate change.

Moving whole communities away from the coastline sounds like a remote possibility. But as sea levels rise, relocation might be an increasingly inevitable, though challenging, option.

Migration is an important means to cope with the impacts of climate-related shocks. Research shows that networks of prior migrants aid this crucial adaptation mechanism.

Rising sea level is a principal threat to coastal systems worldwide — but far from being a simple matter of landscapes doomed to drown, the story involves complex feedbacks with the same processes that threaten them. Now a modelling study shows that the size and shape of tidal estuaries may determine their fate — proffering a perspective for mitigation against future sea-level rise.

Nitrous oxide is a potent greenhouse gas for which global emission estimates, driven largely by fertilizer input, are highly uncertain. An inversion approach based on atmospheric measurements yields global increases more than twice as high as the IPCC default.

Climate change is likely to increase human migration, but future climate-related migration flows will depend heavily on the adaptive capacity of people living in vulnerable regions and on the border policies of potential destination countries. Current opportunities for mobility are constrained by increasingly strict border enforcement and the securitization of international migration.

In this Perspective, the authors argue that defining the climate change problem as one of decarbonization rather than emissions reduction suggests a new guiding metaphor — the global fractal — which may be a more productive conceptualization for research and policy than the global commons.

Model estimates of future hydroclimate are uncertain, especially at the regional scale. This Perspective argues that constraining model runoff and its sensitivity to precipitation and temperature can greatly reduce this uncertainty and improve climate model utility in water resource applications.

Opinions on climate policy in the United States are politically polarized. Here, survey research shows that opinion polarization on the Green New Deal developed rapidly due to decreasing support among Republicans, which was associated with exposure to conservative media and increasing familiarity with the policy.

Natural peatlands accumulate carbon but land-use change and drainage leads to emission of GHGs from peatlands. Loss of natural peatland area globally has shifted the peatland biome from a sink to a source of carbon, but restoration of drained peatlands could make them carbon neutral.

Terrestrial primary productivity will increase with CO₂ fertilization, but water limitation will decrease this positive effect. Analyses of Earth system model projections show that extreme droughts will have a much stronger impact on future productivity than mild and moderate droughts.

Nitrous oxide, a strong GHG, is produced during nitrification. Changes in ocean pH cause its production to increase, relative to nitrification rates, suggesting large potential increases in the future as ocean acidification continues.

The ways in which ocean communities respond to warming are related to their composition. The variety of thermal affinities and thermal ranges of individual species, along with vertical temperature gradients, shape community response and allow the prediction of regional responses to warming.

Qualitative comparative analysis of 25 case studies across climate change hotspots in Africa and Asia shows that male migration and women’s poor working conditions combine with either institutional failure or poverty to constrain women’s agency, which limits their adaptive capacity.

The reflectivity of the Arctic Ocean decreases as sea ice decreases, creating a feedback of more heat absorption, warming and further melt. An ensemble of models is used to gain understanding of this in the current climate to constrain the intermodel spread in predictions of sea-ice albedo changes.

Wind speeds have reduced globally over land since the 1980s. In situ data show that this reversed around 2010, with natural ocean–atmosphere variability thought to drive the wind speed changes, as well as a 17% increase in potential wind energy for 2010–2017 and a boosted wind power capacity factor.

Small shallow estuaries face enhanced flood risk under climate change because of sea-level-rise-induced tidal amplification. In contrast, large deep estuaries are threatened by sediment starvation and therefore a loss of intertidal area. Both cases can potentially be mitigated by estuary widening.

Estimates of N₂O emissions are important given its role as a GHG. Atmospheric inversions indicate emissions increased over the past decade at a rate 2.5 times that estimated using the IPCC default method, and the emissions response to N-input is larger than linear when N-input is high.

In the US, 99.8% of the 459 endangered animals are susceptible to at least one climate change sensitivity factor. Yet analysis of official documents (1973–2018) shows this risk does not translate into action: only 64% of species are considered threatened by climate change, and management planned for 18%.