News & Views in 2021

As temperatures rise, plants unfold their leaves earlier in spring, but whether plant roots respond similarly is seldom quantified. Now, a meta-analysis suggests that leaf and root phenology do not respond to warming in the same way, even within the same plant types.

The climate system may respond in different ways to reductions in atmospheric CO₂ concentrations. Work now shows a delayed recovery (hysteresis) of the tropical rainbelt, with widespread implications for water resources.

Flooding-adaptation studies often ignore unique social, cultural and institutional drivers. Now, research illuminates the drivers that are unique versus shared across socio-cultural contexts and adaptations, which vary in ease of implementation.

Most emissions scenarios in line with the Paris Agreement have shown a large amount of net-negative CO₂ emissions during the second half of this century. A new set of scenarios expands this picture.

Eastward flow in the Southern Ocean is the primary conduit between ocean basins. A comprehensive study of multi-decadal observational records and model experiments reveals that warming in the upper ocean is causing this flow to accelerate.

Finding effective ways to support rural communities in adapting to climate change is critical for building climate-resilient societies. Now research shows the potential of risk-transfer policies for improving adaptation and securing the livelihoods of smallholder farmers.

Climate change is threatening agricultural productivity and the welfare of farmers. Increasing employment in non-farm sectors could mitigate such negative impacts, especially in developing countries.

Assessing the global implementation of climate adaptation is critical. Now, research quantifies where adaptation is happening and where gaps remain.

Southern salmon populations face increased risk from a warming climate. New analysis of salmon ear bones shows outsized reliance on rarely used cold-water habitat for population survival through drought years — habitat that is expected to shrink under climate change.

Improvements in public transport are often regarded as essential to combat climate change. A study investigating the Chinese high-speed rail system suggests that these benefits could operate through channels other than those that one might expect.

Atmospheric rivers substantially affect the global hydrologic cycle, yet their response to past and future anthropogenic forcing remains highly uncertain. New research reveals the counterbalancing effects of aerosols and greenhouse gases and how this balance will shift to favour stronger atmospheric rivers in the coming decades.

Climate change generates multifaceted and difficult-to-measure risks to human and natural systems. Now, research offers a composite indicator of global climate risk that may help track progress in addressing climate change.

Economic models of climate change are the basis for climate policy design. However, incorrect representation of physical dynamics in these models could lead to biased advice.

While earlier reproduction in a great tit population is expected to help with warmer springs, oak tree health seems to influence their ability to modulate their breeding period.

Increased flood risk from climate change requires adaptation, but future protection may leave communities with residual risk that is overlooked. Research now quantifies residual flood damage globally, highlighting the need to lower costs and time to deploy flood management infrastructure, particularly in vulnerable regions.

Observational data from long-term monitoring plots show that the carbon sink of remaining, undisturbed African and Amazonian tropical rainforest is declining. A study now finds that simulations from Earth system models cannot reproduce this decline.

Climate models disagree on how the year-to-year variability of the El Niño/Southern Oscillation will change in a warmer world. Using a high-resolution climate model with an improved tropical Pacific mean state, research now suggests that El Niño activity tends to get weaker under GHG-induced warming.

Changes in river discharge due to climate change are highly uncertain, and a recent study used a global streamflow dataset to assess whether such trends are detectable. Streamflow changes occurred more often in basins impacted by human disturbances than in pristine ones, and there was no clear signal from climate change alone.

Economically optimal climate strategies may be politically less feasible because they need strong collective action. Fortunately, achieving climate goals through more realistic differentiated policies may not be much more expensive.