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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 [...]

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 [...]

Commercial airline flights spend most the time in the lower reaches of the stratosphere, which is the second layer of the atmosphere beginning at five to six miles up in the air. The air in the stratosphere is thin and cold, making it inhospitable, but it is also less turbulent than the air in the [...]

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: Periods of increased stratospheric aerosol content over the past 50 years likely dampened the  warming trend. Volcanic eruptions can cool the Earth by injecting sulfur up into the stratosphere, the second layer of the atmosphere between five and 30 miles in altitude. The volcanoes increase stratospheric levels of tiny droplets of sulfuric acid, [...]

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: Earth’s ocean circulation patterns and  climate would be much different without the presence of the Rocky and Andes Mountains, and without the Antarctic Ice Sheet. A system of big warm and cool water ocean currents, which dwarf the flow of even the largest rivers, work to mix heat and nutrients around the globe. [...]

Trivia Question: True or False: Bacteria can cause rainfall. The correct answer is true. Bacteria are single-celled organisms that are found on every continent, at the bottom of the ocean and as high as 50 miles in the atmosphere. Each year, between 90 million and four billion pounds of bacteria travel from the Earth’s surface [...]

Changes in climate are fundamentally about changes in the amount of energy in the air and water circulating around us. While most discussions of climate trends focus on the air temperature taken at the Earth’s surface, this is only one measure of the amount of energy in the air, let alone the climate system as [...]

In the air around you are organic aerosols – substances based on carbon-hydrogen bonds that are light enough to be suspended in the atmosphere for days or weeks. How much organic aerosol mass is in the air has direct implications for air quality and human health, as well as for climate and weather. Organic aerosols [...]

In Brief: In the eastern United States, afternoon summertime rainfall events are more probable in areas where soil moisture levels are high. Afternoon summertime precipitation in the wet, humid and heavily vegetated eastern United States is related to the evaporation that happens in the morning. Lots of soil moisture can stimulate lots of evaporation, which [...]

In Brief: The boundaries of the Hadley circulation have expanded over the past 30 years, with the most pronounced expansions occurring during the summer months. Earth’s weather is driven largely by the behavior of two large scale tropical circulation systems: the Hadley circulation and the Walker circulation. The Hadley circulation develops as large columns of [...]

In Brief: Earth’s Walker circulations have strengthened over the last 30 years, with wet regions of the circulations getting wetter and dry regions getting drier. Earth’s weather is driven largely by the behavior of two large scale tropical circulation systems: the Hadley circulation and the Walker circulation. The Walker circulation can be broken down into [...]

In Brief: Climate is the dominant force behind changes in river flow on a global scale, despite many other significant contributing factors that must be accounted for when making accurate estimates of water cycle changes. Regional precipitation and temperature changes, atmospheric composition changes that affect plant growth, land use changes, changes in nitrogen deposition on [...]

The northern circumpolar permafrost region –  located mostly above 60 degrees North or the southern tip of Scandinavia – is an area where temperatures are so cold that the soil remains permanently frozen, except for an active surface layer that is as shallow as a few inches deep. Beneath this active layer lie ancient carbon [...]

Commonly known as the biological carbon “pump,” oceans take carbon from out of the atmosphere and deposit it down to the depths. This process is dominated by phytoplankton on the surface taking carbon out of the atmosphere to build their bodies, dying and then falling down to the ocean bottom, where the carbon they originally [...]

Tiny particles suspended in the air affect Earth’s temperature by reflecting, absorbing and scattering solar radiation. These tiny particles known as aerosols – generally between ten billionths and 1000 billionths of a meter –are so small that it only takes slight winds to keep them aloft. In addition to affecting solar radiation, aerosols are also [...]