Volume 10 Issue 4, April 2020

The partisan divide between Republicans and Democrats on climate change is large and shows no signs of narrowing. However, a new analysis shows that Republicans’ climate change attitudes were relatively unstable between 2014–2018, triggering cautious optimism that a tipping point in attitudes might be around the corner.

Future Arctic methane emissions depend partly on interactions between soil carbon released during permafrost thaw and microbial physiology. Now, a model shows potential increased methane produced from thawing permafrost carbon could be offset by increased consumption by upland methanotrophs.

Climate change detection is confounded by internal variability, but recent initial-condition large ensembles (LEs) have begun addressing this issue. This Perspective discusses the value of multi-model LEs, the challenges of providing them and their role in future climate change research.

In order to limit warming and the most severe consequences of climate change, net global carbon emissions must reach zero by 2050. Many ecosystems contain carbon that would be irrecoverable on this timescale if lost and must be protected to meet climate goals.

Climate change and other human activities are decreasing ocean oxygen content. This Perspective considers the limited data on effects to coral reefs, including oxygen thresholds for lethal and sub-lethal effects in coral reef taxa, and proposes key research questions to address this critical issue.

Coal use is responsible for a large proportion of climate damages. This study shows that phasing out coal yields substantial near-term, local environmental and health benefits that outweigh direct policy costs, providing incentives for immediate climate action.

Earth’s energy imbalance from human and natural drivers—effective radiative forcing—is difficult to constrain, contributing to uncertainty in long-term climate change. A top-down observational constraint reduces IPCC AR5 assessed uncertainty by nearly 40% and suggests models are biased low.

Models overestimate Arctic methane emissions compared to observations. Incorporating microbial dynamics into biogeochemistry models helps reconcile this discrepancy; high-affinity methanotrophs are an important part of the Arctic methane budget and double previous estimates of methane sinks.

Climate change beliefs in the US are politically polarized. Using longitudinal survey data, this study finds that climate change beliefs are less stable over time for Republicans compared with Democrats, suggesting that public beliefs may eventually shift towards broader acceptance.

Costs of achieving climate targets are uncertain. A metamodel estimates the median costs of limiting warming to 2 °C and 1.5 °C to be US$15 trillion and US$30 trillion. Uncertainty in emissions reductions costs dominates at these levels; climate system uncertainty dominates at higher warming levels.

Over 60 years of hydrographic data from southeast of Bermuda show the temporal variability of North Atlantic subtropical mode water. Between 2010 and 2018, there was an 86–93% loss of thickness, suggesting weaker production of mode water that is expected to continue with warming.

Exceptionally warm years in 2017–2019 have caused changes in the physical and biological characteristics of the Pacific Arctic Ocean. What these changes mean for the ecosystem and societal consequences will depend on if they are evidence of a transformation or anomalies in the system.

Nitrogen removal occurs primarily through microbially mediated denitrification, which produces the GHG N₂O, and anaerobic ammonium oxidation (anammox), which does not. Warming stimulates denitrification relative to annamox in subtropical sediments, indicating that warming could lead to greater N₂O production.

Changes in the leaf area index alter the distribution of heat and moisture. The change in energy partitioning related to leaf area, increasing latent and decreasing sensible fluxes over the observational period 1982–2016, is moderated by plant functional type and background climate.

Northern peatlands are a significant carbon sink but are vulnerable to decomposition during drought and low water tables. Woody litter added to these ecosystems during high water table conditions leaches polyphenolics that protect carbon stores against decomposition, even during subsequent drought.

Climate change has led to earlier spring leaf-out in northern temperate and boreal regions. This advanced leaf-out causes warming in the Northern Hemisphere due to the combined effects of water vapour, cloud and snow-albedo feedbacks on the surface energy budget.