Weather, Climate, and Paleoclimatology

Posted in 1 on FebruaryUTCbThu, 21 Feb 2008 09:02:47 +0000000000amThu, 21 Feb 2008 09:02:47 +000008 21, 2008 by vincewilltown
climate_paleo.gif, stock photos

What is weather?

Weather is the state of atmospheric conditions (i.e., hot/cold, wet/dry, calm/stormy, sunny/cloudy) that exist over relatively short periods of time (hours to a couple of days). Weather includes the passing of a thunderstorm, hurricane, or blizzard, and the persistence of a heat wave, or a cold snap. Weather variability and extreme events such as floods and droughts, may be an unpredictable response to climate change.

What is Climate?

Climate is the weather pattern we expect over the period of a month, a season, a decade, or a century. More technically, climate is defined as the weather conditions resulting from the mean, or average, state of the atmosphere-ocean-land system, often described in terms of “climate normals” or average weather conditions. Climate Change is a departure from the expected average weather or climate normals.

What is Paleoclimatology?

Paleoclimatology is the study of past climate. The word is derived from the Greek root “paleo-,” which means “ancient,” and the term “climate.” Old Leaf image, stock photo Paleoclimate is that which existed before humans began collecting instrumental measurements of weather (e.g., temperature from a thermometer, precipitation from a rain gauge, sea level pressure from a barometer, wind speed and direction from an anemometer). Instead of instrumental measurements of weather and climate, paleoclimatologists use natural environmental (or “proxy”) records to infer past climate conditions. Paleoclimatology not only includes the collection of evidence of past climate conditions, but the investigation of the climate processes underlying these conditions.

How do we measure paleoclimate?

paleo data image courtesy of NOAA and Paleo Slide SetsAnnual records of climate are preserved in tree-rings, locked in the skeletons of tropical coral reefs, frozen in glaciers and ice caps, and buried in the sediments of lakes and oceans. These natural recorders of climate are called proxy climate data – that is they substitute for thermometers, rain gauges, and other modern instruments used to record climate. By analyzing records taken from trees, reefs, glaciers, sediments, and other proxy sources, scientists can extend our understanding far beyond the 140-year instrumental record provided by thermometers and rain gauges.

Recent changes in the natural record from environmental proxy data can be calibrated using the 140-year instrumental record of climate change.

What can Paleoclimatology tell us about climate change relevant to society in the future?

To understand and predict changes in the climate system, we need a more complete understanding of seasonal to century scale climate variability than can be obtained from the instrumental climate record. The instrumental temperature record indicates that the Earth has warmed by 0.5°C (0.9°F) from 1860 to the present. However, this record is not long enough to determine if this warming should be expected under a naturally varying climate, or if it is unusual and perhaps due to human activities. Paleoclimatic proxy data can be used to extend climate records and provide a longer time frame (hundreds to tens of thousands of years) for evaluating the warming of the last 140 years.

The cause of global warming over the last century remains a heated debate with significant economic and societal implications. Many scientists attribute the current global warming to the enhancement of the greenhouse effect by human activities. Other scientists have suggested that other factors not affected by humans, such as changes in the number and size of volcanic eruptions or an increase in the sun’s output (such phenomena are referred to as climate forcings), are responsible. A paleoclimate perspective provides information about long term changes in different climate forcings that may be the underlying cause of the observed climate change.

An analogy of how paleoclimatic data improves our understanding of climate can be explained in terms of the stock market. Stock market analysts use longer term trends (one, two, three, or six months) in the stock market indexes (DOW, NASDAQ, etc.) rather than depending on changes from one day to the next or over a week to predict what the market will do next (i.e., Bull or Bear Market). In much the same way, the paleoclimate perspective allows us to evaluate climate change many decades and centuries into the past, in order to develop a more reliable estimate of how climate may change in the future.

The paleoclimate perspective can help us answer many questions, including…

  • Is the last century of climate change unprecedented relative to the last 500, 2000, and 20,000 years?
  • Do recent global temperatures represent new highs, or just part of a longer cycle of natural variability?
  • Is the recent rate of climate change unique or commonplace in the past?
  • What does it mean if the last century is unprecedented in terms of warming?
  • Can we find evidence in the paleoclimate record for mechanisms or climate forcings that could be causing recent climate change?


How do we study “Global Warming?”

Posted in 1 on FebruaryUTCbThu, 21 Feb 2008 09:00:42 +0000000000amThu, 21 Feb 2008 09:00:42 +000008 21, 2008 by vincewilltown

icecore image - courtesy of NOAA Paleo Slide Sets There are several ways that scientists study how the Earth’s temperature is changing. Although these methods have some uncertainties, each suggests a similar story – that the Earth has warmed dramatically over the last 140 years and that the Earth is now warmer than it has been in the last 1000 years.

Some scientists look to satellites to reveal something about the Earth’s changing climate. Although the satellite record is very short (ca. 20 years) and hard to interpret due to changes in instruments and orbits, the latest satellite studies confirm the same story – the globe is warming.

The record of instrumental temperature measurements, which extends back to the 19th century, provides one clear indication that the modern earth is warming: divers.gif, photo courtesy of NOAA Paleo Slide Sets that the mean annual surface air temperatures of the earth have risen approximately 0.5°C (0.9°F) since 1860.

Paleoclimatic data, generated from the study of things like tree rings, corals, fossils, sediment cores, pollens, and ice cores, and cave stalactites, both provide an independent confirmation of this recent warming, and place the 19th to 20th century (1860 to present day) warming in a long term context. The paleoclimatic record not only allows us to look at global temperature fluctuations over the last several centuries, it also permits scientists to examine past climate even further back in time over the course of millennia and longer. This perspective is an important capability in our quest to understand the possible causes of the 20th century global warming. We can look at hypothesized warm periods in the distant past (e.g., 1,000; 6,000; 125,000; and even 165,000,000 years ago) to see if they provide clues for natural processes that could be causing the global warming we are now experiencing. So far, paleoclimatologists have been unable to find any natural climatic explanations for our present-day warming.

Global Warming

Posted in 1 on FebruaryUTCbThu, 21 Feb 2008 08:59:09 +0000000000amThu, 21 Feb 2008 08:59:09 +000008 21, 2008 by vincewilltown

What is Global Warming?

sun.jpg, photo courtesy of NOAA Photo Library
The term Global Warming refers, without any implications for the cause or magnitude, to the observation that the atmosphere near the Earth’s surface is warming. This warming is one of many kinds of climate change that the Earth has gone through in the past and will continue to go through in the future.

Why is Global Warming important?

Temperature increases will have significant impacts on human activities, including: where we can live, what food we can grow, how and where we can grow food, and where organisms we consider pests can thrive. To be prepared for the effects of these potential impacts we need to know how much the Earth is warming, how long the Earth has been warming, and what has caused the warming. Answers to these questions provide us with a better basis for making decisions related to issues such as water resources and agricultural planning.

What is the Greenhouse Effect?

Greenhouse effect image Our planet absorbs radiant energy from the sun and emits some of that energy back to space. The term greenhouse effect describes how water vapor, carbon dioxide, and other “greenhouse” gases in the atmosphere alter the return of energy to space, and in turn, change the temperature at the Earth’s surface. These greenhouse gases absorb some of the energy that is emitted from the Earth’s surface, preventing this energy from being lost to space. As a result, the lower atmosphere warms and sends some of this energy back to the Earth’s surface. When the energy is “recycled” in this way, the Earth’s surface warms.

Life on Earth would be very different without the greenhouse effect. The greenhouse effect keeps the long term annual average temperature of the Earth’s surface approximately 32°C (or about 58°F) higher than it would be otherwise.

How is the Greenhouse Effect related to Global Warming?

Greenhouse gases occur naturally in the Earth’s atmosphere, but are also being added by human activities. This happens primarily through the burning of fossil fuels, such as coal, oil and natural gas, which releases carbon dioxide to the atmosphere. Over the past century, atmospheric carbon dioxide (as measured from ice cores) has increased due to human activities from 300 to 380 parts per million (ppm), and the average Earth temperature has increased approximately 0.7°C (or about 1.3°F).

Co2 image
Given what we know about the ability of greenhouse gases to warm the Earth’s surface, it is reasonable to expect that as concentrations of greenhouse gases in the atmosphere rise above natural levels, the Earth’s surface will become increasingly warm. Many scientists have now concluded that global warming can be explained by a human-caused enhancement of the greenhouse effect.

It is important to remember both that the greenhouse effect occurs naturally, and that it has been intensified by humankind’s input of greenhouse gases into the atmosphere.

Are Ozone Holes related to Global Warming or the Greenhouse Effect?

ozone.gif, photo courtesy of NASA The formation of ozone holes is related to these scientific issues, yet is still distinct.
Ozone plays a very important, natural role in the upper atmosphere (called the stratosphere), where 90% of it exists. Stratospheric ozone acts as a shield against harmful ultraviolet (UV) radiation from the sun. This ozone can be destroyed by human-produced chemical compounds called chlorofluorocarbons, or CFCs. When these CFCs are combined with extremely cold stratospheric temperatures over the poles, solar radiation, and particular patterns of atmospheric circulation, chemical reactions occur that cause “Ozone Holes” over Antarctica (pictured above) and the Arctic.

The formation of ozone holes is related to global warming and the greenhouse effect in two ways. First, CFCs are greenhouse gases. Thus, the release of these compounds into the atmosphere will have two separate effects: to destroy ozone and to add to the greenhouse effect. Second, if stratospheric temperatures or patterns of atmospheric circulation change as part of global warming, this will affect the chemical reactions that destroy ozone and cause the ozone holes to either grow or shrink.

Global Warming

Posted in Global disaster with tags on FebruaryUTCbThu, 21 Feb 2008 08:45:00 +0000000000amThu, 21 Feb 2008 08:45:00 +000008 21, 2008 by vincewilltown

The photograph taken in 1928, above, shows how the Upsala Glacier, part of the South American Andes in Argentina, used to look. The ice on the Upsala Glacier today, shown in 2004 below, is retreating at least 180 ft. per year