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Recent observed global warming is significantly less than that simulated by climate models. This difference might be explained by some combination of errors in external forcing, model response and internal climate variability.
The City of Los Angeles is nearly two thirds of the way towards its goal of generating a third of its electricity from renewable sources by 2020; cities around the world can glean valuable technical, economic and political lessons from its experience.
Can we achieve the ambitious mitigation targets needed to avert dangerous global warming? Research now shows that local sanctioning institutions may succeed where global agreements fall short.
The effects of climate change on the extremes of rainfall and the associated floods and droughts have been well documented. Analysis now provides evidence that rainfall seasonality is also changing in some parts of the tropics, which has important implications for ecological as well as human systems.
Using model ensembles for simulating the responses of future crop yields to climate change offers the prospect of more reliable projections, but requires sustained international collaboration and exchange of high-quality data for model testing.
Climate change poses both practical and theoretical problems for coastal managers, who have to make and implement plans that cope with a highly uncertain, and therefore inherently risky, future. This Perspective uses three examples of ecological engineering — marshes, mangroves, and oyster reefs — to illustrate the synergistic effects and benefits of this approach.
Since the 1950s—after centuries of stock decline and deforestation—European forests started to recover, becoming a persistent carbon sink. The effect was projected to continue for decades, however there are early signs that the sink is saturating. This Perspective calls for a timely reaction from policymakers and forest managers to sustain European forests and thus the carbon sink.
Climate change cooperation has been limited by the lack of sanctioning mechanisms to deal with those who fail to abide by agreements. Research now shows that a bottom-up process, in which parties create local institutions that punish free-riders, promotes widespread cooperation as opposed to the traditional top-down approach that builds global institutions.
Flood losses in coastal cities will rise due to increasing populations and assets. Research now quantifies average losses in the 136 largest coastal cities. Estimated at approximately US$6 billion in 2005, average annual losses could increase to US$52 billion by 2050 on the basis of projected socio-economic change alone. If climate change and subsidence are also considered, current protection will need to be upgraded to avoid unacceptable losses.
The impact of climate change on the global hydrological cycle is unclear, with land precipitation and river discharges not increasing as expected. This discrepancy is investigated and tropospheric aerosols are found to have weakened the hydrological cycle between the 1950s and 1980s. The increase in greenhouse gases since the 1980s strengthened the cycle, indicating a further increase in precipitation if the current trend continues.
Climate change is altering the seasonal distribution, interannual variability and overall magnitude of precipitation. A new global measure of precipitation seasonality is proposed, and application of this method to observations from the tropics shows that increases in variability were accompanied by shifts in seasonal magnitude, timing and duration.
Flood risk is expected to increase as the climate warms. This study, for the first time, uses several climate models to estimate the global risk of flooding at the end of the century. Projections show a large increase in flood frequency in some areas, whereas other regions can expect a decrease. Vulnerability is dependent on the degree of warming and the interannual variability in precipitation.
The El Niño/Southern Oscillation exhibits considerable natural variability on interdecadal to centennial timescales making it difficult to understand how climate change affects it. A reconstruction now shows there has been anomalously high activity in the late twentieth century, relative to the past seven centuries. This is suggestive of a response to global warming, and will provide constraints to improve climate models and projections.
Large standardized model intercomparison projects enable the quantification of uncertainty in projecting the impacts of climate change. One of the largest studies so far indicates that individual crop models are able to simulate wheat yields accurately under a range of environments, but that differences between crop models are a major source of uncertainty.
Climate change is expected to increase the intensity of precipitation in many regions. Experiments show that small increases in precipitation intensity, but not total amount, can lead to deeper penetration of water into the soil, leading to greater woody plant growth at the cost of grasses in a savannah system.
Competing influences on tropical forest productivity, such as changes in temperature, light and precipitation, can be difficult to disentangle. Now, analysis of how clouds, temperature and precipitation affect flower production in two contrasting tropical forests indicates that temperature is a critically important variable for tropical forest flower production.
Little is known about the sensitivity of Antarctic krill, a key part of the food chain, to ocean acidification. A circumpolar risk map of krill hatching success is presented for projected ocean acidification levels. Important krill recruitment habitats are likely to become high-risk this century, with the possibility of collapse of the krill population by 2300 without mitigation of CO2 emissions.
The hydrological cycle influences the development of societies, as well as human lifestyles and well-being across the globe. How climate change might affect the timing and variability of precipitation, along with the resulting floods and droughts, could significantly impact agriculture, water resources and natural ecosystems. In this web focus we present a variety of articles, including original research, that highlight trends in precipitation and flooding under climate change.
