Sea ice impacts most of the Arctic environment, from ocean circulation and marine ecosystems to animal migration and marine transportation. Sea ice has thinned and decreased in age over the observational record. Ice extent has decreased. Reduced ice cover has warmed the surface ocean, accelerated coastal erosion and impacted biological productivity. Declines in Arctic sea-ice extent cannot be explained by internal climate variability alone and can be attributed to anthropogenic effects.

Whether or not an increase in meltwater will make ice sheets move more quickly has been contentious, because water lubricates the ice–rock interface and speeds up the ice, but also stimulates the development of efficient drainage; now, a long-term and large-area study of a land-terminating margin of the Greenland Ice Sheet finds that more meltwater does not equal higher velocity.

The El Niño/Southern Oscillation (ENSO) influences global climate as well as extreme weather events such as floods, droughts, and tropical cyclones, leading to large societal impacts globally have shown that El Niño—the warm phase of ENSO—effectively discharges oceanic heat into the central to eastern North Pacific basin through the subsurface ocean after its wintertime peak, resulting in high tropical cyclone activity during the following tropical cyclone peak season in the eastern North Pacific, which has significant implications for seasonal prediction of tropical cyclone activity in the

The pens slipped easily across the paper, about every eight minutes. At regular intervals, Heads of State entered the innermost sanctum and solemnly signed their names, committing their nations to the Framework Convention on Climate Change. The year, 1992. The place, the landmark United Nations Conference on Environment and Development, known as the “Earth Summit” at Rio de Janeiro.

The recent decline in Horn of Africa rainfall during the March–May “long rains” season has fomented drought and famine, threatening food security in an already vulnerable region. Some attribute this decline to anthropogenic forcing, whereas others maintain that it is a feature of internal climate variability. We show that the rate of drying in the Horn of Africa during the 20th century is unusual in the context of the last 2000 years, is synchronous with recent global and regional warming, and therefore may have an anthropogenic component.

Earlier spring leaf unfolding is a frequently observed response of plants to climate warming. Many deciduous tree species require chilling for dormancy release, and warming-related reductions in chilling may counteract the advance of leaf unfolding in response to warming. Empirical evidence for this, however, is limited to saplings or twigs in climate-controlled chambers.

Glacial erosion is fundamental to our understanding of the role of Cenozoic-era climate change in the development of topography worldwide, yet the factors that control the rate of erosion by ice remain poorly understood. In many tectonically active mountain ranges, glaciers have been inferred to be highly erosive, and conditions of glaciation are used to explain both the marked relief typical of alpine settings and the limit on mountain heights above the snowline, that is, the glacial buzzsaw.

We examine the response of Arctic sea ice to projected aerosol and aerosol precursor emissions changes under the Representative Concentration Pathway (RCP) scenarios in simulations of the Canadian Earth System Model. The overall decrease in aerosol loading causes a warming, largest over the Arctic, which leads to an annual mean reduction in sea ice extent of approximately 1 million km2 over the 21st century in all RCP scenarios. This accounts for approximately 25% of the simulated reduction in sea ice extent in RCP 4.5, and 40% of the reduction in RCP 2.5.

Many tropical countries are exceptionally vulnerable to changes in rainfall patterns, with floods or droughts often severely affecting human life and health, food and water supplies, ecosystems and infrastructure. There is widespread disagreement among climate model projections of how and where rainfall will change over tropical land at the regional scales relevant to impacts, with different models predicting the position of current tropical wet and dry regions to shift in different ways.