I do not know much about global warming the fact is, the temperature down southern United States is much worse than 90 degree Fahrenheit and near it is around 100 degree Fahrenheit. I also noticed the heat wave across the Europe and Asia. If you still want to be outdoor when the temperature is very hot, I suggest you bring a big water bottle, stay away from the direct sun light and feel free to sit under a nice big tree shade.

Here is a simple way to explain the global warming effect. Just notice the temperature differences between a car before and after the sun light hit on it. If you do not let the windows down the heat will trap inside the car and it will get warmer as day goes by. If you put a sun shade on your windshield to reflect the sunlight it will definitely reduce the temperature significantly. The same concept applied to the earth. When at night it is cool due to lack of sun light, the gas in the atmosphere is cool and unexcited. During day time extra sun light (UV rays) reached to the earth due to ozone depletion and heat up some gases in the atmosphere. But, there is no way for them to escape.

Previously mentioned is just one factor effecting the global warming. There are many other factors involved in global warming such as human made gases (CO2, CFC and other earth unfriendly gases), climate changes and etc,. If you need additional information please visit U.S. Environmental Protection Agency website at http://www.epa.gov