The beginning of widespread instrumental meteorological observations in the 18th century heralded the start of climatological record-keeping. By the mid- to late 19th century the economic benefits of these records became obvious. Winds, currents, and waves delineated (and still do) optimum shipping lanes. Temperature and precipitation regimes largely determine the limits of practicality for agriculture and water resources. During this century and the next, the climatic data will be necessary, directly or indirectly, to achieve sustainable economic advantages in virtually every enterprise in America. During the late 1980s and early '90s, the most conspicuous reporting of climate issues involved global warming via the greenhouse effect and stories relating to catastrophic storms like hurricanes Hugo, Andrew, and Fran. Beyond the headlines and behind the scenes, however, tens of thousands of economic decisions are being made each day with the aid of climatic information.
Whereas weather chiefly concerns the present and near-term future state of the atmosphere, climate accounts for all past weather events as well as the future (in the form of climate model predictions). If you assume that climate is not changing rapidly, then high quality long-term climatic data can tell you the qualitative range of weather events to be expected in the future, and can provide useful quantitative assessments of the likelihood of various weather conditions over the next several years. The National Climatic Data Center is the official repository for the United States' collection of global weather records.
Weather summary for Kansas City Downtown Airport for February 13, 2000:
|
|
|
|
|
|
|
|
Maximum and Minimum values for February:
| Highest temp on record | Lowest temp on record | Max Precip (inches) |
|
|
|
|
Normal values for February:
| Max.Temp | Min. Temp | Precipitation |
|
|
|
|
Based on official USWB/NWS data. The normals are for KCI. Originally compiled by Allen Pearson
(http://www.wdaftv4.com/waindex.htm).
Chart showing the average annual global temperatures
Do Exercise A
Note: In doing this exercise, you'll be looking at and manipulating data in computerized Excel spreadsheets. You may experience a 'Memory Error' when trying to access the Excel spreadsheets while Netscape is running. If this should occur, close Netscape prior to opening the Excel spreadsheets.
The historical record is a powerful tool in our understanding of changes in climate. But is the window of last 100 years or so a wide enough scope at looking at the whole range of potential changes? Many of us have heard of the "Ice Ages" and know that Earth's climate has changed more dramatically over time frames on the order of tens of thousands of years.
Research has provided important insights into the natural factors that caused major changes in the climates of the past. These factors tend to cause modest climate fluctuations on time scales of years to centuries and large- scale changes on time scales of millennia and longer.
Graph showing fluctuations in global ice volume over geologic time
Long periods of worldwide climatic cooling took place over tens of millions of years before the beginning of glaciation. Once ice sheets started to grow, they probably contributed to their own further development. This positive feedback occurred because ice sheets reflect more sunlight back into space than the ground reflects when it is not covered by ice. In other words, ice has a higher "albedo" than a vegetated or barren surface has. The reflected sunlight would've otherwise warmed the Earth's surface. Consequently, the presence of ice sheets may have led to more cooling and continued development of ice sheets.
The position of the continents is probably one of the most important factors controlling long periods of multiple glaciations. The presence of large land masses at high latitude appears to be a prerequisite for the development of extensive ice sheets, because the large accumulations of ice associated with ice sheets cannot form over the ocean. The processes of continental drift and plate tectonics has over the Earth's geologic history moved the continents toward and away from the poles.
(Source of figure: An online text on plate tectonics is This Dynamic Earth from the USGS library. (http://pubs.usgs.gov/publications/text/dynamic.html))
Plate tectonics probably also contributes to the development of long periods with many glaciations by producing large mountain ranges. These mountains have disrupted global oceanic and atmospheric circulation patterns. Changing circulation patterns cause climate change. The uplift of the Himalayas and the Tibetian Plateau probably contributed to the initiation of the current cool period.
Decreases in the amount of carbon dioxide in the atmosphere may lead to global cooling. Many processes can cause a long-term decrease in the amount of CO2 in the atmosphere. These processes include many complex interactions among organisms, ocean currents, erosion, and volcanic activity. Important relationships exist between ice ages and the composition of the atmosphere; however, many scientists are unsure whether the changes in atmosphere cause cool periods or whether cool periods cause atmospheric changes. Also, many scientists are not sure that the magnitude of past CO2 changes was large enough to initiate ice ages.
The advances and retreats of glaciers within an ice-house phase of Earth history is probably in response to changes in Earth's orbit through time. Important parameters that vary include the shape of the orbit around the sun, the tilt of the Earth's axis, and the Earth's wobble. Variation in these three factors changes the amount and distribution of incoming solar radiation. Variations in the distribution of solar radiation can change the climate and lead to ice advances.
Do Exercise B
(The following discussion is an excerpt and modification from a websit exhibit entitled "The Midwestern U.S. 16,000 years ago" at the Illinois State Museum http://www.museum.state.il.us/exhibits/larson/content.html).
During the last major glaciation (the last Ice Age) about 18,000 years ago much of the midwestern U.S. was under a great expansive continental ice sheet. Both summer and winter temperatures were colder than today.
By 16,000 years ago the glaciers were shrinking in size and retreating to the north leaving behind bare ground. Large lakes formed as water melting from the ice was dammed behind sediment-ridges (moraines) deposited from the glaciers. Dust storms were depositing thick layers of silt (called loess) over many areas. Because of the cooler climate, many of the plants and animals that inhabited the area around 16,000 years ago were different than those found in the area today.
Map of the
retreat of the glaciers in the Midwestern U.S. from the last glacial 18,000
years ago (produced by the Illinois State Musuem GIS Laboratory at http://www.museum.state.il.us/research/GISlab/)
kya = thousands of years ago
18,000
years ago
14,000
years ago
12,000
years ago
10,000
years ago
8,000
years ago
Photograph by Dr. Richard Gentile, UMKC Geosciences Dept.
Extensive, thick loess deposits generally formed in areas bordering large, continental glaciers. Large volumes of meltwater flowed from the edges of these glaciers during the summer. This meltwater carried large amounts of sediments that formed as the glacier ground the bedrock over which it moved. Much of this sediment was silt-sized material known as rockflour. During the winter, when the glacier did not melt, the area where the water flowed was dry. The winter winds would pick up the rockflour from these dry areas and carry it long distances in huge dust storms.
When the wind slowed, the silt would fall out and blanket the area. Frequently the resulting loess deposits are several meters thick (tens of feet). Because the source of the silt is the outwash from the glaciers, loess deposits are frequently most extensive and thickest downwind from large river valleys.
Often several different loess deposits are stacked on top of each other in an area because each glaciation causes the formation of a loess deposit. The midwestern U.S. has numerous examples of multiple loesses deposited in the same place. Approximately thirty percent of North America has one or more loesses deposited over the bedrock.
Evidence buried in loess and glacial lakes indicates that there was wide shifts in vegetation that occurred between the last glacial maximum around 18,000 years ago and present.
Spruce logs are found frequently in bog, lake, and loess deposits in much of the midwestern U.S. The section of spruce log pictured above was found in a borrow pit in Illinois. This log was part of tree in a forest that was overridden by glaciers during the last major glacial advance in central Illinois (approximately 20,000 years ago).
Two types of poplars, balsam poplar and quaking aspen have been recovered at sites in the midwestern U.S. Today these two species are common in the high northern latitudes and Rocky Mountain areas of North America.
Most of what we know about these animals comes from sites that date between 40,000 and 10,000 years ago (the last Ice Age). This is because sites older than 40,000 years old are less common than younger sites. Some of the now extinct mammals include the mastodon, the saber-toothed tiger and the ground sloth.
Here ISM Curator of Geology Dr. Jeffrey J. Saunders excavates two mastodon thigh bones at Boney Spring, Benton Co., MO. The bones collected at Boney Spring were deposited between 17,000 and 13,000 years ago. An Illinois State Museum publication by Dr. Saunders discusses the animals that have been found at Boney Springs and other Missouri Spring Sites.
This map shows some of the sites at which the American mastodon has been found in the midwestern United States. The sites on this map are all relatively well-dated and well-studied. These sites contain mastodon remains that are between 40,000 and 10,000 years old. This map was produced using the FAUNMAP database developed and housed at the Illinois State Museum.
(Faunmap at http://www.museum.state.il.us/research/faunmap/aboutfaunmap.html)
Many scientists think that these climatic and ecosystem changes caused the extinction at the end of the Pleistocene. The environmental changes might have caused extinction by eliminating food sources, disrupting birth schedules, or exposing animals to climatic conditions to which they were not adapted.
Theory 2: Human hunters!
The animated figure below shows a simplified example of how the spread of humans could have interacted with the distribution of now extinct animals.
Just after 12,000 years ago human migrants from Asia entered the New World. They may have been the first people to set foot in North America. They are known as the Clovis people. Their sites and artifacts, including distinctive projectile points, are found over much of North America. These people hunted and gathered wild animals and plants. The animals they hunted included many that went extinct. However, they also hunted numerous animals that survived.
This is an excellent example of a Clovis projectile point. It was found at the Kimmswick Site, Jefferson Co. Missouri. The point was found associated with the bones of American mastodons by a crew under the directorship of Illinois State Museum Curator of Geology Dr. Russell W. Graham.
Many scientists think that these people caused the extinction in North America at the end of the Pleistocene. Researchers who support this view generally favor one of two explanations. The first is that human over-hunting directly caused the extinction. The second is that over-hunting eliminated a "keystone species" (usually the mammoths or mastodon) and this led to environmental collapse and a more general extinction.
Do Exercise C
Changes in climate can bring extended drought, inundation of lowlands by sea level rise, damaging torrential rains, adverse affects to agriculture and livestock production, damage structures and populations, and other environmental changes. These conditions can have enormous ecological, economic, social, and political consequences. In 1988 the United Nations Environment Programme and the World Meteorological Organization established an international panel to assess the scientific data on climate change. The most recent report of the Intergovernmental Panel on Climate Change (IPCC) in 1995 concluded that human activities are increasing global warming.
"The 1990s have been a time of international soul- searching about the environment. What are we doing to our planet? More and more, we are realizing that the Industrial Revolution has changed forever the relationship between humanity and nature. There is real concern that by the middle or the end of the next century human activities will have changed the basic conditions that have allowed life to thrive on earth." UNEP
"The most direct result, says the scientific consensus, is likely to be a "global warming" of 1 to 3.5°C over the next 100 years. That is in addition an apparent temperature increase of around half a degree Centigrade since the pre-industrial period before 1850, at least some of which may be due to past greenhouse gas emissions. "
Climate Policy The UN's Intergovernmental Panel on Climate Change suggested global policy should be enacted to mitigate climate change. Such measures include: (1) reduction of fossil fuel dependency, (2) increase energy efficiency, (3) preservation of forests, and (4) conversion to renewal energy sources, for example, wind and solar energy.
The United Nations Framework Convention on Climate Change that went into effect in March 1994 was ratified by 160 countries, including the U.S. This treaty sets an "ultimate objective" of stabilizing "greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic (human-induced) interference with the climate system.". It directs that "such a level should be achieved within a time-frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in a sustainable manner."
The choice of time horizon strongly influences the relative importance assigned to current emissions of each greenhouse gas. The Intergovernmental Panel on Climate Change (IPCC) calculates GWPs for three reference time horizons: 20, 100, and 500 years (see figures below). The 20-year horizon is relevant to short-term impacts, such as changes in weather patterns; the 100-year horizon applies to longer time-scale changes, such as sea-level rise; while 500 years represents the longest time-scale it is felt reasonable to consider given our current knowledge. On short time-scales, 1990's CO2 emissions contribute over half the direct effects of 1990's total greenhouse gas emissions, and methane almost 30%. However, because methane has such a short life-time, the relative importance of 1990 methane emissions becomes much less for longer time horizons.
Under a "Business as Usual" scenario (i.e. no changes in current policies), the group forecast a 0.3 C-per-decade rise in global mean temperature and a six-centimeter-per-decade rise in the average sea level. It also indicated how different regions of the world could be affected by these developments.
In December 1997, the third United Nations Framework Convention on Climate Change will take place in Kyoto, Japan. The main goal of the conference is to establish specific guidelines to reduce greenhouse gas emissions after the year 2000.
In the United States, citizens and businesses have rallied into groups both for and against setting limits on energy consumption. The Environmental Protection Agency (EPA) efforts are concentrated fuel efficiency, reduction of the emission of greenhouse gases produced by fossil fuel burning, and alternative energy sources.
The purpose of the visualization effort of the GENESIS Earth System Modeling Project is to aid in the analysis of global climate research and communicate its findings through the creation of animations. In the summer of 1994, the first coupled atmosphere-vegetation simulation was conducted with GENESIS to investigate climate change from increasing CO2 levels. Input to the model was supplied by extrapolating historic CO2 increases out 300 years into the future. Model results for temperature increase, precipitation and forest coverage are shown.
Atmospheric carbon dioxide concentration increasing to six times pre-industrial levels by 2300 A.D. was the basis for the following model results.
Resultant temperature change, shown for January and July monthly averages in the Northern hemisphere by the year 2300 A.D.
Resultant precipitation change, shown for January and July monthly averages in the Northern hemisphere by the year 2300 A.D.
Vegetation changes in North America showing the constriction of temperate
forests and poleward migrations. Pink is dead forest; light green is new
forest.
Do Exercise D
GENESIS visualization climate change models http://www.cgd.ucar.edu:80/ccr/
GLOBE Visualization http://globe3.gsfc.nasa.gov/cgi-bin/home.cgi
NASA Goddard DAAC (Distributed Active Archive Center) http://daac.gsfc.nasa.gov/
NASA Mission to Planet Earth http://www.earth.nasa.gov
Climate Visualization Tools http://covis.atmos.uiuc.edu/geosciences/visualization/climate.html
Kansas City Weather Almanac http://www.wdaftv4.com/waindex.htm
Illinois State Museum Midwestern U.S. 16,000 Years Ago Exhibit http://www.museum.state.il.us/exhibits/larson/content.html