Earth Gauge » Global Climate Change Impacts Report

Climate Fact: Heat Waves

kraus — Mon, 23 Aug 2010 14:13:53 +0000

In Brief: Nights are warmer than they were in the early 1970s, which exacerbates the urban heat island effect and heat related health problems.

Heat waves – which in the United States kill up to 1,000 people per year – are defined as prolonged periods of abnormally hot weather. They can occur at any time of the year. What “abnormally hot” weather is will vary from place to place and from season to season, making a standard range of dangerous temperatures difficult to determine. What’s more, people become acclimated to seasonal temperatures. This means that sudden onsets of summer weather early in the year are generally much more dangerous than equivalent temperatures later in the summer. Some basic human physiological limits, however, can provide set temperatures that are dangerous. Heat index temperatures of 130 degrees Fahrenheit or higher are considered extremely dangerous, with heat stroke or sunstroke likely. Temperatures between 105 and 129 degrees are in the danger zone, when sunstroke, muscle cramps, and/or heat exhaustion likely. Heatstroke is possible with prolonged exposure and/or physical activity. When the heat index is between 90 and 105 degrees, extreme caution with the heat is recommended.

Because they are built with heat trapping materials like concrete and asphalt, cities tend to be hotter than surrounding rural areas. This is particularly true at night, when cool temperatures are important for giving the body a break from the heat. Urbanization, in addition to a general warming trend, means that extreme heat events are becoming more common. In North America over the last 50 years, average nighttime low temperatures have risen faster than average daytime high temperatures. There has been a 50 percent increase in the number of unusually warm nights, and nights with temperatures that would have fallen into the top tenth percentile during the 1950s now fall into the top fifteenth percentile. Almost all of this increase has happened since 1975.

Seasons: Spring, Summer, Fall

Sources: Meisner, BN. “Heat Wave.” National Weather Service Southern Region Homepage. NOAA. 15 May 2000. Accessed Online 16 August 2010 and United States Climate Change Science Program. “Weather and Climate Extremes in a Changing Climate.” Synthesis Assessment Product 3.3: GPO. 2008 and American Red Cross. “Talking about Disaster: Guide for Standard Messages.” Available from: and Centers for Disease Control. “Tips for Preventing Heat Related Illness.” Accessed Online 16 August 2010

Climate Fact: Climate and North Atlantic Hurricanes

kraus — Fri, 04 Sep 2009 17:50:51 +0000

The torrential rainfall and storm surges associated with hurricane landfall events can cause what are known as “overwash deposits” that leave definitive marks in the sediment layers that accumulate in coastal areas. Analyses of sediment cores from various locations along the Eastern Seaboard and Puerto Rico show that for the last 1500 years, Atlantic Hurricanes are more frequent when a) the El Niño-Southern Oscillation is in a La Niña phase, which reduces the amount of vertical wind shear over the North Atlantic and b) the North Atlantic is relatively warm, which usually coincides with positive phases of the Atlantic Multidecadal Oscillation. Over the 20th century, ocean temperatures in the North Atlantic main development region warmed during peak hurricane season, with the most pronounced warming occurring over the last four decades.

To view the chart of 20th century North Atlantic main development region peak hurricane season SST’s visit: http://www.earthgauge.net/climate-facts-image-library#6. This image is featured in the “Global Climate Change Impacts in the United States” report recently published by the U.S. Global Change Research Program. The image is in the public domain.

Seasons: Summer, Fall

Sources: Global Climate Change Impacts in the United States, Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson, (eds.). Cambridge University Press, 2009 and Mann, ME et al. “Atlantic hurricanes and climate over the past 1,500 years.” Nature 460 (2009): 880-883.

Climate Fact: Seasonal Rainfall in the Southeast

kraus — Wed, 26 Aug 2009 17:01:53 +0000

Over the second-half of the 20th century, the Southeast experienced an overall decline in annual rainfall levels along with a 20 percent increase in the frequency of extreme (top first percentile) rainfall events. Looking at the 20th century as a whole, there have been significant changes in the seasonal distribution of precipitation, with strong increases in the amount of precipitation in the fall, noticeable decreases in the winter and slight declines during the spring and winter months.

To see how the seasonality of rainfall has changed in your local area, visit http://www.earthgauge.net/climate-facts-image-library#8. This image is featured in the “Global Climate Change Impacts in the United States” report recently published by the U.S. Global Change Research Program. The image is in the public domain.

Seasons: Winter, Spring, Summer, Fall

Source: Global Climate Change Impacts in the United States, Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson,(eds.). Cambridge University Press, 2009

Climate Fact: Winter Temperatures and Crop Yields

kraus — Wed, 26 Aug 2009 16:49:50 +0000

Many of America’s most important commercial crops require between 400 and 1800 hours each winter when the temperature is below 45 degrees Fahrenheit. Winter temperatures have been rising steadily across the nation, with the most pronounced trends being witnessed in the upper-Midwest and Northeast. In fact, winter temperatures are rising faster than temperatures in any other season.

To see how winter temperatures are changing in your area, visit http://www.earthgauge.net/climate-facts-image-library#7. This image is featured in the “Global Climate Change Impacts in the United States” report recently published by the U.S. Global Change Research Program. The image is in the public domain.

Season: Winter

Source: Global Climate Change Impacts in the United States, Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson,(eds.). Cambridge University Press, 2009.

Climate Fact: Temperatures and Crop Yields

kraus — Wed, 26 Aug 2009 16:45:02 +0000

In North America over the last 50 years, average nighttime low temperatures have risen faster than average daytime high temperatures. There has been a 50 percent increase in the number of unusually warm nights and nights that fell into the top tenth percentile in terms of temperature for the climate of the 1950’s now fall into the top 15th percentile. Increases in daily minimum temperatures mean that crops are using more water for evaporation in order to keep cool, which decreases the amount of water the plants use producing edible parts. Snap peas, for example, show marked reductions in production once the nighttime temperature rises above 80 degrees Fahrenheit. When daily maximum temperatures become too hot, plants like corn and soybean will not grow as well. Corn will not reproduce when temperatures are above 95 degrees and soybeans will not reproduce when temperatures exceed 102 degrees.

To view how corn and soybeans respond to given temperatures, visit http://www.earthgauge.net/climate-facts-image-library#7. This image is featured in the “Global Climate Change Impacts in the United States” report recently published by the U.S. Global Change Research Program. The image is in the public domain.

Seasons: Spring, Summer

Source: Global Climate Change Impacts in the United States, Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson,(eds.). Cambridge University Press, 2009

Climate Fact: Spring Snowmelt in the West

kraus — Wed, 26 Aug 2009 16:19:07 +0000

About 75 percent of the West’s water resources originate in snowpack. Most precipitation in the region occurs during the winter, the period of the year when the reservoirs are replenished after the dry summer and early fall months. The reservoirs are at their high points in the spring. Traditionally, snowpack would last into the late spring and summer months, and not overwhelm the already full reservoirs in the early to mid-spring. Since the 1950’s however, there has been a steady trend of earlier snowmelt across the West, causing the rivers to start their spring snowmelt “pulse” sooner. If the rivers peak too soon, in order to keep the dams from breaking water from the reservoirs must be discharged instead of being conserved for the summer months. In some parts of the West, the average date of the start of the spring streamflow “pulse” is now happening over 20 days earlier than it did in the 1950’s.

To see how spring snowmelt timing has changed in your local area since the 1950’s, visit http://www.earthgauge.net/climate-facts-image-library#9. This image is featured in the “Global Climate Change Impacts in the United States” report recently published by the U.S. Global Change Research Program. The image is in the public domain.

Seasons: Spring

Source: Global Climate Change Impacts in the United States, Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson,(eds.). Cambridge University Press, 2009

Climate Fact: National Annual Precipitation Trends (Arizona)

kraus — Wed, 26 Aug 2009 15:36:27 +0000

Most areas of the United States are now receiving more total annual rainfall than they did 50 years ago. There is significant regional variability in this trend, however. Adding up the total regional positive and negative trends, the U.S. as a whole is now receiving five percent more precipitation each year. The Northeast and northern Midwest have shown the greatest increases in average annual rainfall, with the Southeast and Southwest exhibiting the greatest rainfall reduction trends. Some of the Nation’s most pronounced rainfall reduction trends have occurred in Arizona. While most of the state has experienced around five percent reduction in annual rainfall levels, parts of the southwest corner of the state have witnessed as much as a 40 percent drop.

To see how average annual precipitation has changed in your local area since the 1950’s, visit http://www.earthgauge.net/climate-facts-image-library#8. This image is featured in the “Global Climate Change Impacts in the United States” report recently published by the U.S. Global Change Research Program. The image is in the public domain.

Seasons: Winter, Spring, Summer, Fall

Source: Global Climate Change Impacts in the United States, Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson,(eds.). Cambridge University Press, 2009

Climate Fact: National Annual Precipitation Trends (Georgia)

kraus — Wed, 26 Aug 2009 15:34:09 +0000

Most areas of the United States are now receiving more total annual rainfall than they did 50 years ago. There is significant regional variability in this trend, however. Adding up the total regional positive and negative trends, the U.S. as a whole is now receiving five percent more precipitation each year. The Northeast and northern Midwest have shown the greatest increases in average annual rainfall, with the Southeast and Southwest exhibiting the greatest rainfall reduction trends. Some of the Nation’s most pronounced rainfall reduction trends have occurred in Georgia, where there has been a statewide five to 15 percent decrease in total annual rainfall.

Seasons: Winter, Spring, Summer, Fall

Source: Global Climate Change Impacts in the United States, Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson,(eds.). Cambridge University Press, 2009

Climate Fact: National Annual Precipitation Trends (South Carolina)

kraus — Wed, 26 Aug 2009 15:31:01 +0000

Most areas of the United States are now receiving more total annual rainfall than they did 50 years ago. There is significant regional variability in this trend, however. Adding up the total regional positive and negative trends, the U.S. as a whole is now receiving five percent more precipitation each year. The Northeast and northern Midwest have shown the greatest increases in average annual rainfall, with the Southeast and Southwest exhibiting the greatest rainfall reduction trends. Some of the Nation’s most pronounced rainfall reduction trends have occurred in South Carolina, where there has been a statewide 10-20 percent decrease in total annual rainfall.

Seasons: Winter, Spring, Summer, Fall

Source: Global Climate Change Impacts in the United States, Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson,(eds.). Cambridge University Press, 2009

Climate Fact: Local Sea-Level Rise (Gulf Coast)

administrator — Tue, 25 Aug 2009 19:37:09 +0000

While global sea-level is rising at a rate of about 1.2 inches per decade due to an influx of glacial melt water and thermal expansion of the oceans, the relative sea-level rise or fall that each coastal location experiences is dependent on several factors. Local sea-level can rise faster than the global average due to subsidence of the land. It can rise slower than the global average or even fall if uplift of the land occurs at a sufficient pace. Along parts of Alaska’s coast, for example, sea-levels are falling as land that was pushed down by the weight of glaciers has “rebounded” as ice has melted. Changes in ocean circulation, which can shift wind and wave patterns, can also cause relative changes in sea-level. The Gulf Coast has witnessed some of the fastest rates of sea-level rise in the country. Here, 27 percent of roads, nine percent of railways and 72 percent of ports are built on land less than four feet above sea-level.

For the accompanying visual, visit http://www.earthgauge.net/climate-facts-image-library#6. This image is featured in the “Global Climate Change Impacts in the United States” report recently published by the U.S. Global Change Research Program. The image is in the public domain.

Seasons: Winter, Spring, Summer, Fall

Source: Global Climate Change Impacts in the United States, Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson,(eds.). Cambridge University Press, 2009.

Climate Fact: Local Sea-Level Rise

administrator — Tue, 25 Aug 2009 19:23:28 +0000

Seasons: Winter, Spring, Summer, Fall

Source: Global Climate Change Impacts in the United States, Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson,(eds.). Cambridge University Press, 2009.

Climate Fact: Extreme Heat in Phoenix

administrator — Tue, 25 Aug 2009 19:11:03 +0000

While Phoenix has always been hot for U.S. standards, over the last 50 years the city has been getting even hotter. The average number of days per year when the temperature is over 100 degrees has doubled over this time period. Part of this is likely due to the Urban Heat Island effect, which has grown as the area’s concrete cover has expanded. Arizona leads the Nation in heat related deaths, at three to seven times the national average.

For the accompanying visual, visit http://www.earthgauge.net/climate-facts-image-library#3. This image is featured in the “Global Climate Change Impacts in the United States” report recently published by the U.S. Global Change Research Program. The image is in the public domain.

Seasons: Summer

Source: Global Climate Change Impacts in the United States, Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson,(eds.). Cambridge University Press, 2009.

Climate Fact: National Annual Precipitation Trends

administrator — Fri, 21 Aug 2009 14:27:23 +0000

Seasons: Winter, Spring, Summer, Fall

Source: Global Climate Change Impacts in the United States, Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson,(eds.). Cambridge University Press, 2009

Climate Fact: Drought Trends

administrator — Wed, 19 Aug 2009 15:04:08 +0000

As Earth warms, the water cycle intensifies. While this means more total rainfall for some regions, it also means that more rainfall comes in the form of heavy and extreme events and periods between rainfall events become longer. Longer periods without rain and higher temperatures lead to losses of soil moisture; if drying of the soil continues for long enough, droughts occur. Since the 1950’s, some areas of the United States, including most of the Northeast and Midwest, have been experiencing drought conditions less frequently. Other areas, including most of the West and Southeast, have been experiencing drought conditions more often.

To see how drought frequency has changed in your local area since the 1950’s, visit http://www.earthgauge.net/climate-facts-image-library#3. This image is featured in the “Global Climate Change Impacts in the United States” report recently published by the U.S. Global Change Research Program. The image was originally created as part of an ongoing analysis of drought trends by Guttman and Quayle (see citation below). The image is in the public domain.

Seasons: Summer, Fall

Sources: Global Climate Change Impacts in the United States, Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson,(eds.). Cambridge University Press, 2009 and Guttman, NB and Quayle, RG. “A historical perspective of U.S. climate divisions.” Bulletin of the American Meteorological Society 77 (1996): 293-303. Operational practices described in this paper continue.

Climate Fact: Stagnant Air and Heat Waves

administrator — Mon, 17 Aug 2009 14:32:35 +0000

Heat waves, defined as three or more consecutive days when temperatures exceed 90 degrees Fahrenheit, can create public health hazards. In the United States, heat and drought account for the biggest share of hazard-related deaths at 19.6 percent. Death rates rise an average of six percent during heat waves and over the 20th century, the average number of heat waves doubled across the United States. Lack of rainfall and the prevalence of stagnant air conditions when there is little or no wind both work to compound the problem. Over the second half of the 20th century throughout most of the West, the southern Great Plains and the Southeast, stagnant air conditions were prevalent more the 25 percent of the time during heat waves.

To see how frequent stagnant air conditions are in your local area, visit http://www.earthgauge.net/climate-facts-image-library#1. This is a public domain image from the recently published “Global Climate Change Impacts in the United States” report published by the U.S. Global Change Research Program. The data used came from the NOAA’s National Climatic Data Center.

Season: Summer

Sources: Global Climate Change Impacts in the United States, Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson,(eds.). Cambridge University Press, 2009 and Patz, JA. et al. “Impact of regional climate change on human health.” Nature 438 (2005): 310-317.