Mean surface global temperatures have increased by 0.5-1.0°F since the late 19th century. The 20th century's 10 warmest years all occurred in the last 15 years of the century. Of these, 1998 was the warmest year on record. The snow cover in the Northern Hemisphere and floating ice in the Arctic Ocean have decreased. Globally, sea level has risen 4-8 inches over the past century. Worldwide precipitation over land has increased by about one percent. The frequency of extreme rainfall events has increased throughout much of the United States. So what we witness now is global warming climate.

Increasing concentrations of greenhouse gases are likely to accelerate the rate of climate change. Scientists expect that the average surface global temperatures could rise by 1-4.5°F (0.6-2.5°C) in the next fifty years, and 2.2-10°F (1.4-5.8°C) in the next century, with significant regional variation. Evaporation will increase as the climate warms, which will increase average global precipitation. Soil moisture is likely to decline in many regions, and intense rainstorms are likely to become more frequent. Sea level is likely to rise two feet along most of the U.S. coast.

As you may see scientists blame greenhouse effect for global warming. And consequently we, mankind, are blamed for greenhouse effect. Carbon dioxide , a cause of greenhouse effect, is so to say a side action of in man-made devices such as automobiles and power plants. But Robert Essenhigh, E.G. Bailey Professor of Energy Conservation in Ohio State's Department of Mechanical Engineering says that it is the rising global temperatures that are naturally increasing the levels of carbon dioxide, not the other way around. Essenhigh believes that we should also take into consideration great amount of carbon dioxide that enters and leaves the atmosphere as part of the natural cycle of water exchange from, and back into, the sea and vegetation. "Many scientists who have tried to mathematically determine the relationship between carbon dioxide and global temperatures would appear to have vastly underestimated the significance of water in the atmosphere as a radiation-absorbing gas," Essenhigh argues. "If you ignore the water, you're going to get the wrong answer."

Some scientists believe that the human contribution to carbon dioxide in the atmosphere, however small, is of a critical amount that could nonetheless upset Earth's environmental balance. But Essenhigh feels that, mathematically, that hypothesis hasn't been adequately substantiated.

In 1973 Cambridge University geologists Nicholas Shackleton and Neil Opdyke published a repot in the journal Quaternary Research. They stated that global temperatures have been oscillating steadily, with an average rising gradually, over the last one million years - long before human industry began to release carbon dioxide into the atmosphere. According to Shackleton and Opdyke's data, average global temperatures have risen less than one degree in the last million years, though the amplitude of the periodic oscillation has now risen in that time from about 5 degrees to about 10 degrees, with a period of about 100,000 years.

Nowadays Essenhigh states that we are simply near a peak in the current cycle that started about 25,000 years ago. And Russian scientists from the Russian Sciences Academy Observatory have analyzed the Sun's radiation fluctuations that influence the climate on Earth and the results have shown that the planet at the moment is on the peak of the global warming process. They predict that starting from 2012 we will witness a reverse process of global temperatures - cooling.