How do we study "Global Warming?
There are several ways that scientists study how the Earth's temperature is changing. Although each method has some uncertainties, they all suggest 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 600 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, extending back to the 19th century, provides one clear indication: that the mean annual surface air temperatures of the earth have risen approximately 0.5°C (0.9°F) since 1860. 
Paleoclimatic data provides an independent confirmation of this recent warming, and also places the 19th to 20th century (1860 to present day) warming in the context of the last several centuries to millennia. 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. 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.
Find words and phrases in the article which have similar meaning to 1 to 10
1  quite a few                          2 propose    
3 radically                               4 difficult   
 5 because of                           6 corroborate
7 sign                                      8 average    
9 increased                            10 about

Questions
1 What do all  the various research studies show?
2 How old are satellite records?
3 Why are they difficult to read?
5 What other records are there?    How old are they?
6What contribution does Paleoclimatic  data give to the global warming issue ?
Weather, Climate, and Paleoclimatology

What is weather? 

Read the text below and underline the definition of 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 may be an unpredictable response to climate change. 
What is Climate? 
Read the text below and underline the definition of climate
Climate is the weather 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 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." Paleoclimate is climate that 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 you measure temperature ? 
How do you measure rainfall? 
How do you measure pressure? 
How do you measure wind velocity? 

	
How do we measure paleoclimate? 
Annual 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. 
Where can you find “proxy” records 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. 
Has the Earth warmed in the last century and a half? 
If so,  by how much?

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 greenhouse effect enhanced by human activities. Other scientists have suggested that other factors are responsible, such as natural 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). A paleoclimate perspective provides information about long term changes in different climate forcings that may be the underlying cause of the observed climate change. 
Do scientists agree on the cause of recent global warming?
What are some of the possible causes?
What are the climate forcings?