Since the weather is Since the weather is getting hotter and getting hotter and hotter today, I am hotter today, I am going to talk about the going to talk about the causes of the unusually causes of the unusually weather.weather.

Past Climate ChangePast Climate Change The Earth's climate has The Earth's climate has

changed throughout history. changed throughout history. From ice ages where ice From ice ages where ice covered significant portions covered significant portions of the Earth to ice ages of the Earth to ice ages where ice retreated to the where ice retreated to the poles or melted entirely - the poles or melted entirely - the climate has continuously climate has continuously changed.changed.

Recent Climate Recent Climate ChangeChange

Since the Industrial Revolution (around Since the Industrial Revolution (around 1750), human activities have 1750), human activities have substantially added to the amount of substantially added to the amount of heat-trapping greenhouse gases in theheat-trapping greenhouse gases in the atmosphere. The burning of fossil fuels atmosphere. The burning of fossil fuels and biomass (living matter such as and biomass (living matter such as vegetation) has also resulted in vegetation) has also resulted in emissions of aerosols that absorb and emissions of aerosols that absorb and emit heat, and reflect light.emit heat, and reflect light.

The addition of greenhouse gases and aerosols has changed the composition of the atmosphere. The changes in the atmosphere have likely influenced temperature, precipitation, storms and sea level. However, these features of the climate also vary naturally, so determining what fraction of climate changes are due to natural variability versus human activities is challenging.

The following pages provide a summary of the atmosphere and climate changes observed during the Industrial Era and, where possible, current understanding of why the changes have occurred .

Atmosphere ChangesAtmosphere Changes The release of greenhouse gases The release of greenhouse gases

and aerosols resulting from and aerosols resulting from human activities are changing human activities are changing the amountthe amount. . of radiation coming of radiation coming into and leaving the into and leaving the atmosphere, likely contributing atmosphere, likely contributing to changes in climate.to changes in climate.

Greenhouse Gases Greenhouse gas concentrations in the

atmosphere have historically varied as a result of many natural processes (e.g. volcanic activity, changes in temperature). However, since the Industrial Revolution humans have added a significant amount of greenhouse gases in the atmosphere by burning fossil fuels, cutting down forests and other activities. Because greenhouse gases absorb and emit heat, increasing their concentrations in the atmosphere will tend to have a warming effect. But the rate and amount of temperature increase is not known with absolute certainty.

Temperature ChangesTemperature Changes Temperatures are Temperatures are

changing in the lower changing in the lower atmosphere - from the atmosphere - from the Earth’s surface all the way Earth’s surface all the way through the stratosphere through the stratosphere (9-14 miles above the (9-14 miles above the Earth’s surface). Scientists Earth’s surface). Scientists are working to document are working to document temperature trends and temperature trends and determine their causes.determine their causes.

Sea Level Changes

Sea levels are rising worldwide and along much of the U.S. coast. Tide gauge measurements suggest that sea level has risen worldwide approximately 6-8 inches (15-20 cm) during the last century . A significant amount of sea level rise has likely resulted from the observed warming of the atmosphere and the oceans.

People around the world may feel People around the world may feel that the climate has been getting that the climate has been getting steadily warmer and warmer in steadily warmer and warmer in recent years. Places which used to be recent years. Places which used to be abundant in snowfall have abundant in snowfall have frequently experienced snowfree frequently experienced snowfree winters. Drought lasts longer in winters. Drought lasts longer in some dry areas. People find that some dry areas. People find that without air conditioners they could without air conditioners they could hardly work or fall asleep on hotter hardly work or fall asleep on hotter summer days.summer days.

It is apparent that all the It is apparent that all the changes caused by global changes caused by global warming is related to human’s warming is related to human’s bad behavior.bad behavior.

Global warming, I think, is Global warming, I think, is not far away from us, it has not far away from us, it has already changed our lives. The already changed our lives. The temperature in shanghai for temperature in shanghai for example, is higher in May than example, is higher in May than average. So we have lost part average. So we have lost part of the spring. of the spring.

To stop global warming we should make immediate and continual efforts. I hope the situation will soon change. Global warming catches and holds our concern, for it affects us and will affect our later generations. We cannot wait any longer. Do it. Do it right. Do it right now.