Subscribe Now

In terms of total annual rainfall, most of the United States became “wetter” over the 20th century. Most of this increase, however, is being expressed in “extreme” rainfall events, which are now more frequent and even more extreme than they were in the 1950s. In the Great Plains, for example, the amount of rain that [...]

The El Niño-Southern Oscillation, the periodic “sloshing” back and forth of warm water between the eastern and western tropical Pacific, is believed to affect the frequency of tropical cyclone development in the North Atlantic. Specifically, during La Niña phases (when the waters off the west coast of South America are unusually cool) circulation in the [...]

In terms of total annual rainfall, most of the United States became “wetter” over the 20th century. Most of this increase, however, is being expressed in “extreme” rainfall events, which are now more frequent and even more extreme than they were in the 1950s. In the Southeast, for example, the amount of rain that falls [...]

In terms of total annual rainfall, most of the United States became “wetter” over the 20th century. Most of this increase, however, is being expressed in “extreme” rainfall events, which are now more frequent and even more extreme than they were in the 1950s. In the upper-Midwest, for example, the amount of rain that falls [...]

In terms of total annual rainfall, most of the United States became “wetter” over the 20th century. Most of this increase, however, is being expressed in “extreme” rainfall events, which are now more frequent and even more extreme than they were in the 1950s. In the Northeast, for example, the amount of rain that falls [...]

Increases in water vapor in the stratosphere (the second layer of the atmosphere extending from about ten to 30 miles in altitude) has implications for ozone, stratospheric temperatures, and surface temperatures. While more water vapor in the stratosphere leads to ozone depletion there and a slight cooling of surface temperatures, this cooling is more than [...]

In the Atlantic, the frequency of hurricane formation and the strength of the storms that form during a given year are controlled by things like Atlantic sea surface temperatures, temperature differences between the eastern and western tropical Pacific (i.e. the El Niño-Southern Oscillation) and even things like dust storm frequency in the Sahara Desert. On [...]

Over the past four decades, there has been a planet-wide lengthening of the “green” period between leaf emergence in the spring and leaf drop in the fall, which is now about 15 days longer than it was in 1970. This lengthening has been linked to the planet’s warming trend. Just as changes in climate can [...]

A 1000 year record of sediment samples taken from Lower Mystic Lake (near Boston, MA) and four centuries of historical records chronicling weather events, land use changes and the relative abundance of different plant species, have been used to estimate the relative frequency of hurricanes over the past millennia. Historical records indicate that seven hurricane [...]

Temperature records from a suburb north of Los Angeles indicate that periods of three consecutive days when the temperature exceeds 90 degrees Fahrenheit (events commonly referred to as “heat waves”) are more common now than they were 100 years ago. Specifically, by the end of the 20th century, each year featured on average three more [...]

Forest ecosystems are composed of a variety of species with a variety of tolerances for different climatic conditions. As climatic conditions change, some species become more prevalent, some become less prevalent, and some disappear altogether. In the Amazon Basin, for example, paleobotanical records show that drier conditions favor the survival of grasses and shrubs over [...]

Over the last century, the frequency of both heavy (95th percentile) and very heavy (99th percentile) precipitation events rose by 14 and 20 percent, respectively. Over this same period, the relative contributions of heavy and very heavy rainfall to annual precipitation totals increased by 1.6 and one percent, respectively. Since 1895, America’s average temperature has [...]

How many storms and how severe the storms are that strike the California Coast (most storms strike during the winter months) appears to be largely controlled by two multiannual oscillations: The Pacific Decadal Oscillation (PDO) and the El Niño Southern Oscillation (ENSO). During warm phases of the PDO, the heat in the North Pacific is concentrated [...]

The El Niño-Southern Oscillation (ENSO), or the cyclical movement of heat in the tropical Pacific Ocean, affects atmospheric phenomena throughout the world. The cycle affects the strength and position of the Pacific Jet Stream, an upper atmosphere wind current that flows from the Pacific over North America. During La Niña phases of the cycle, the [...]

The El Niño Southern Oscillation (ENSO) cycle, or the cyclical movement of heat in the tropical Pacific Ocean, affects the upper atmosphere over the Atlantic Ocean. This affects both the frequency of Atlantic tropical cyclone formation as well as the positioning of the region’s high and low pressure centers that steer the tropical cyclones. La [...]

The tropical Pacific basin is one of the planet’s warmest ocean regions, with surface water temperatures rarely falling below 83 degrees Fahrenheit. These perennially warm temperatures provide the fuel for tropical cyclone formation, and the strongest cyclones on record have formed here. Because these waters are already above the threshold for tropical cyclone formation, slight [...]

Convective available potential energy (CAPE) is a measure of how much energy is available for storm development (CAPE is measured by the number of joules present in a kilogram of air). Generally, the hotter and more humid conditions are, the more CAPE is present. A collection of atmospheric conditions, including some CAPE, are necessary for [...]

The northeastern quadrant of the contiguous United States, defined here as the area from Minnesota south to Missouri and then east to Maryland and north to Maine, has been experiencing changes in its precipitation regime. While the average annual number of “wet” days (or days when rain falls) in that region declined by about four [...]

The summer of 2003 was one of Europe’s warmest on record and maximum sea surface temperatures (SSTs) in the Mediterranean were well above average (by about 2.5 degrees Fahrenheit). These temperatures were the highest recorded between 1972 and 2004.  Also during this period, years when the maximum water temperature was above average were years when [...]

Getting a break from exposure to hot temperatures is important for preventing heat related illnesses. While people usually associate extreme daytime temperatures with heat stroke, if it does not cool sufficiently during the night, the body will not get a break from the heat. In North America over the last 50 years, average nighttime low [...]