Quote:

---

hmmm i wonder how they know what the climate and weather was like that far back?

---

Quote:

---

SOURCES OF CLIMATE HISTORY

Records of local weather, made with the help of meteorological instruments, cover at most about two hundred years, and an even shorter span if a truly global picture is desired. Other, historical accounts exist for individual places--most notably in China, where for certain sites they extend back two thousand years. But although these records are useful, more extensive information is required to understand the full range of natural climate variability.

Laboratory analyses of geologic sediments and other layered materials help meet this need, extending what is known of surface temperature, precipitation, and other meteorological parameters many thousands and even millions of years into the past. Many of these tools rely on the fact that plants and other forms of life respond in distinctive ways to changes in the local environment, thus preserving an indirect, or proxy record, of climatic conditions.

Annual growth rings in trees, for example, can be read much like a diary: tree-ring widths tell of seasonal variations of local air and water conditions--as does the chemical composition of the wood within each ring. The presence of forests and other vegetation, which are indicators of climatic conditions, can be reconstructed from the analysis of pollen in lake sediments. Cores extracted from the floor of the ocean allow us to examine in fossil form the microscopic life that once lived near the ocean surface, and through this analysis, to recover information about the temperature of the ocean many millions of years ago. The extent and composition of coral reefs are indicators of tropical ocean temperatures and, through changes in ocean salinity, of local precipitation.

A particularly powerful technique of recent years has been the recovery and analysis of ice cores, about ten cm (four inches) in diameter and as much as two miles long, drawn from the permanent glaciers on Greenland and Antarctica. Similar samples have been retrieved from high mountain glaciers in South America and Asia. As in the case of trees, the ice is composed of annual layers, although the temporal resolution degrades systematically from top to bottom in the deepest cores.

The analysis of the hydrogen and oxygen in the extracted ice core provides a continuous index of temperature from as far back as 200,000 years ago, sampling conditions in the air above the ice sheet and in the nearby oceans from which the water was evaporated, to later fall as snow. As the snow accumulates, over the years, the underlying layers are compressed into ice. Windblown dust and the residue of ancient volcanic eruptions can also be analyzed. Bubbles entrapped in the ice during the process of compaction preserve samples of fossil air, affording an opportunity for precise measurement of the amount of carbon dioxide (CO2), methane (CH4), and other greenhouse gases in the global atmosphere of long ago.

These techniques are calibrated against similar samples from the present day, for which temperature and other climatic variables are measured directly. What is learned is often limited, as are modern weather station records, to conditions at one region. However, measurements of CO2 and CH4 taken from isolated cores give a global picture, since these long-lived gases are uniformly distributed in the global atmosphere.

When combined, these various forms of paleo-data allow us to reconstruct an imperfect but ever-clearer picture of the climate of the past. All of them clearly indicate that climate varies, due to natural causes, on all time scales, from decades to millions of years.

---

Quote:

---

"I promise to do everything in my power to achieve energy independence ... and to stop global warming," Pelosi said.

---

Quote:

---

Humans cause global warming, US admits

---

Quote:

---

The earth has been warming gradually for 10 thousand years before that it was cooling before that it was warming.

So good luck to those evangelicals, Pelossi and general electric. They can try to restore the "balance of nature" but they are chasing a chimera.

---