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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 [...]

Discussions of climate and climate variability often focus on temperature trends at the Earth’s surface, which is where humans spend most of their time. But the atmosphere holds onto little energy compared to the oceans – the top few feet of the ocean holds as much heat as the entire atmosphere above it! Transfers and [...]

Temperatures have warmed by an average of two degrees Fahrenheit over Earth’s land surface and 0.6 degrees Fahrenheit over the oceans over the past 50 years. These temperature changes have been accompanied by changes in precipitation and seasonal cycles, including lengthening of the growing/frost-free season in temperate and high latitudes. Together, these factors related to [...]

The September/October Arctic sea ice annual minimum this year was the second lowest minimum on record for the 33 year period of satellite observations. The lowest minimum was recorded in 2007. But how do these ice extents relate to what the sea ice has done over the past several hundred or thousand years? Known relationships [...]

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 [...]

The Earth holds more heat today than it did in 1950 and the lion’s share of this heat has been absorbed by the world’s oceans. Water has a higher specific heat than air or land surfaces, meaning that it takes more energy to raise the temperature of a certain amount (say, a pound) of water [...]

Paleoclimatology, the study of past climates and past climate changes, provides ample evidence that climate change can happen suddenly. Around 18,700 years ago, a section of the slowly melting Laurentide (North American) Ice Sheet, which at one point extended all the way from the Arctic to the Ohio River, disintegrated around present day Wisconsin. This [...]

Each year the United States pumps about 28 cubic miles of water out its groundwater aquifers – natural underground storage areas – for irrigation, drinking water, industrial purposes, etc. While about 84.6 percent of these withdrawals are recharged to the aquifers through natural recharge (primarily rainfall) or artificial recharge (recharge to the groundwater from human [...]

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 [...]

Average global sea level is rising by about three millimeters per year. There are three main contributors to this rise, each of which separately account for about one millimeter each: the thermal expansion of water, or the fact that warmer waters occupies more space than cooler water; the melting of mountain glaciers and ice caps; [...]

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 [...]

Earth does not orbit the Sun in a perfect circle. Instead, like all the other planets, Earth’s orbit is eccentric, meaning that it moves in a “stretched out” or elliptical pattern. The difference between the perihelion, the point of an orbit when a planet is closest to the sun, and the aphelion, the point of [...]

The Canadian Arctic Archipelago (CAA), which lies across Baffin Bay from the northwest coast of Greenland, holds about one third of Earth’s ice mass, excluding the giant Greenland and Antarctic Ice sheets. The Archipelago’s 36,500 islands cover 540,000 square miles including Baffin Island, the world’s fifth largest island covering close to 200,000 square miles. The [...]

How do sea levels vary as the world warms or cools? A warmer planet means more heat is stored in the oceans. More heat causes thermal expansion that pushes ocean waters onto the land. A warmer Earth also means more melting of the ice sheets and alpine glaciers that sit on the land surface, putting [...]

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 [...]

The three to seven year El Niño-Southern Oscillation (ENSO) is the periodic warming (El Niño phase) and cooling (La Niña phase) of the eastern tropical Pacific. This warming and cooling is related to a relaxing (El Niño) and strengthening (La Niña) of an upwelling of cold, nutrient rich water from the depths to the surface [...]

Imagine a parcel of warm and salty water travelling northward through the North Atlantic Ocean. As it moves, it gradually loses water through evaporation into the atmosphere – this water creates rain in faraway places. As evaporation happens, the parcel of water becomes saltier and denser. By the time it gets to Greenland, it is [...]

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 [...]

Since 1992, satellites have been providing continuous global coverage of changes in ocean surface heights. The first satellite to provide such coverage, TOPEX Poseidon, was launched in 1992. Although only designed to serve for three years, it provided data until 2005. Jason I, TOPEX Poseidon’s replacement, began operating in 2001 and Jason II was launched [...]

Earth’s lakes are collecting and storing more heat than they did a century or even several decades ago. One indication of this increased heat storage is a global reduction in the annual duration of lake ice cover. In mid-latitude lakes, the average annual date when enough ice has grown to cover a lake’s surface is [...]