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The extent of the Arctic sea ice, which is usually gauged by its annual minimum extent in September, has been declining by 11.2 percent per decade since 1979. Large-scale effects of this decline impact Earth’s climate, primarily through increased absorption of sunlight by the open oceans. Local effects have also been documented. As ice has [...]

In Brief: The recent weakness in the East African long rains has been linked to persistently elevated temperatures in the western tropical Pacific. Rains in East Africa primarily fall during the long rains (March through May) and the short rains (October through December). Understanding how climate and climate change influence these rains is particularly important [...]

In Brief: Variability in North Pacific atmospheric circulation systems affects the timing and strength of the upwelling that occurs along the California Coast, impacting the productivity of the waters there. Earth’s ocean is mixed by a complex system of currents. Downwellings occur when currents move water from the surface to the depths and upwellings occur [...]

Two large scale circulation patterns, the Arctic Oscillation and the El Niño-Southern Oscillation, have proven useful for predicting winter weather in different areas of the United States. AO: The Arctic Oscillation (AO) is the difference in atmospheric pressure between the Arctic and the mid-latitudes of the Northern Hemisphere. Upper-atmospheric westerly winds and mid-latitude winter storms [...]

In Brief: Warmer winter temperatures are allowing the Purple Finch to winter 433 miles farther north than it did in the 1960s. Observers during recent annual Audubon Christmas Bird Counts are noticing different birds in their local areas during the winter months than observers did in the 1960s. Between 1966 and 2005, significant northward movement [...]

In Brief: Warmer winter temperatures are allowing the American Goldfinch to winter 250 miles farther north than it did in the 1960s. Observers during recent annual Audubon Christmas Bird Counts are noticing different birds in their local areas during the winter months than observers did in the 1960s. Between 1966 and 2005, significant northward movement [...]

In Brief: Warmer winter temperatures are allowing the House Finch to winter 270 miles farther north than it did in the 1960s. Observers during recent annual Audubon Christmas Bird Counts are noticing different birds in their local areas during the winter months than observers did in the 1960s. Between 1966 and 2005, significant northward movement [...]

In Brief: African aerosols are transported across the Atlantic, affecting the climate of the Amazon rainforest. Dust suspended in the air and smoke from fires make up most of the aerosol concentrations found in the air around us. Aerosols affect how much sunlight reaches the Earth’s surface and how clouds form, which means they can [...]

In Brief: Plants, particularly in the Amazon, influence their climate by moving moisture from the soil into the atmosphere – less when the soil is dry and more when the soil is wet. This helps to maintain both wet and dry rainfall regimes. Every place in the world has its own climate with its own [...]

In Brief: Glaciers, a key source of water in the West, are melting more in the summer than they are growing during the winter. The glaciers that make the peaks of the Western United States white year round are located almost exclusively within National Forests and National Parks. In addition to providing scenery and tourist [...]

In Brief: The extent of older Arctic sea ice, or ice that has survived at least one melt season, has been declining since 1980 with a melt rate acceleration beginning around 2002. The 2007 September Arctic sea ice minimum extent was the smallest on record. This ice has been in a declining trend since 2002, [...]

In Brief: Warmer July-August temperatures in high-elevation meadows of the southern Rocky Mountain region lead to mid-summer periods where flowers and nectar are scarce, potentially impacting generalist pollinators like bumblebees and the Broad-tailed Hummingbird. After the snow melts in high-elevation meadows of the central Rocky Mountain region, pollinators hatch and flowers bloom. Flowers need pollinators [...]

In Brief: Semi-periodic shifts in North Pacific sea surface temperature distributions have been linked survival rates of Coho Salmon off the Pacific Northwest coast. Water conditions along the Pacific Northwest coast are controlled by the Northern California Current (NCC) system, which features a strong alongshore northward flow of warm waters during winter and a southward [...]

In Brief: Warmer temperatures are prompting species to expand their breeding ranges towards the poles. Compared to the 1970s, the Kentucky Warbler’s mean breeding range latitude is now about 88 miles farther north, while the mean latitude of the Golden-Winged Warbler’s breeding range is about 136 miles farther north. Range, the geographic area where a [...]

In Brief: Warmer temperatures are prompting species to expand their breeding ranges towards the poles. Compared to the 1970s, Swainson’s Thrush now has a mean breeding range latitude 88 miles farther north and the Blue-gray Gnatcatcher has a mean breeding range 195 miles farther north. Range, the geographic area where a species is located, can [...]

In Brief: Sunlight reflecting off snow covered forest floors gives extra energy to boreal forest trees as they come out of their winter dormancy. Boreal (Northern Hemisphere) spring is here. Even in the high northern latitudes, temperatures are beginning to warm and plants are beginning to come out of dormancy and photosynthesize, using the Sun’s [...]

Meteorological spring is defined as the March, April and May period. Astronomically, it is defined as the period from around March 21 to June 21. On March 21, day and night are of equal length everywhere on the globe. From March 21 to June 21, the days get longer in the Northern Hemisphere and shorter [...]

In Brief: The more work Northern Hemisphere tropical cyclones do during the summer and fall to move energy from the tropics to the poles, the less energy there is to move during the winter months. The 2010 Atlantic hurricane season ended on November 30th, but Earth’s climate still “remembers” the tropical storms that formed during [...]

Mid-latitude regions in the Northern Hemisphere, like the United States, are now experiencing short days and cold temperatures. In Australia, in the Southern Hemisphere, days are long and temperatures are warm. The farther away from the poles you go, the less difference there is between winter and summer. At the equator there are about 12 [...]

Like humans, birds can freeze when temperatures get too low – but unlike people, birds can’t go inside and turn the thermostat up during the winter. Once food starts to disappear and temperatures drop in the fall, many birds travel to someplace warmer with more food. Some birds fly thousands of miles from their summer [...]