The issues of global warming and climate change have long been a source of controversy in political circles, but in a U.S. Environmental Protection Agency 2012 Updated Report, scientists conclude that Earth's climate is indeed changing. Temperatures are rising, snow and rainfall patterns are shifting, and more extreme climate events –like heavy rainstorms and record high temperatures—are already affecting society and ecosystems. The report indicates scientists are now confident that many of the observed changes in the climate can be linked to the increase in greenhouse gases in the atmosphere, caused largely by people burning fossil fuels to generate electricity, to heat and cool buildings, and to power vehicles.

An independent study conducted by the University of Lisbon predicts 'mega-heat waves' like the one estimated to have killed tens of thousands in Western Europe in 2003 will become up to 10 times more likely over the next 40 years. The study further reveals that the Eastern European heat wave of 2010 blamed for the deaths of many people and for devastated crops in multiple countries was the worst since records began and led to the warmest summer on the continent for at least 500 years.

While critics and supporters of global climate change on both sides of the fence argue about the reasons for the changing weather, the latest and ongoing research leaves little doubt that the climate is affecting many changes, especially in agriculture. According to the updated 2012 EPA report, greenhouse gas concentrations in the atmosphere will continue to increase unless the billions of tons of annual emissions decrease substantially.

The study projects that increased concentrations of greenhouse gases are expected to increase Earth's average temperature, influence the patterns and amounts of precipitation, reduce ice and snow cover (as well as permafrost) raise sea levels, and increase the acidity of the oceans. Researchers say these changes will affect food supplies, water resources, infrastructure, ecosystems, and human health in the years ahead.

The study further indicates the magnitude and rate of future climate change will primarily depend on a number of factors, including: the rate at which levels of greenhouse gas concentrations in the atmosphere continue to increase; how strongly features of the climate –such  as temperature, precipitation, and sea level—respond to the expected increase in greenhouse gas concentrations; and, just as importantly, natural influences on climate—from volcanic activity and changes in the sun's intensity and natural processes within the climate system, such as changes in ocean circulation patterns.

According to the latest European study at Leeds and Reading, by the 2020s, hot days are expected to occur over large areas of Western Europe where previously they were uncommon, and unless farmers find ways to combat the heat stress that damages seed formation, yields of maize in France, for example, could fall by 12 percent compared to today.

The studies are the first global assessment of a range of climate change impacts—from increased flooding to rising demand for air conditioning—of how cutting carbon emissions could reduce these impacts.