today's day, global warming is main problem of our country. Global warmingis a slow steady rise in Earth's surfacetemperature.
Temperatures today are 0.74 °C (1.33°F) higher than 150years ago.
Many scientists say that in the next 100–200 years, temperatures might be up to 6 °C (11 °F) higher than they were before the effects of global warming were discovered.
Climate change has happened many times over the history of the Earth, including the coming and going of ice ages. For more recent centuries, we have more details. Since the 1800s, people have recorded the daily temperature. By about 1850, there were enough places measuring temperature so that scientists could know the global average temperature.
Some people try to stop global warming, usually by burning less fossil fuel. Many people have tried to get countries to emit less greenhouse gases. The Kyoto Protocol was signed in 1997. It was meant to reduce the amount of greenhouse gases in the atmosphere to below their levels in 1990. However, carbon dioxide levels have continued to rise.
During the middle Holocene, some 5,000–7,000 years ago, conditions appear to have been relatively warm indeed, perhaps warmer than today in some parts of the world and during certain seasons. For this reason, this interval is sometimes referred to as the Mid-Holocene Climatic Optimum. The relative warmth of average near-surface air temperatures at this time, however, is some what unclear. Changes in the pattern of in solation favoured warmer summers at higher latitudes in the Northern Hemisphere, but these changes also produced cooler winters in the Northern Hemisphere and relatively cool conditions year-round in the tropics. Any overall hemispheric or global mean temperature changes thus reflecteda balance between competing seasonal and regional changes.