The Proceedings of the National Academy of Sciences researchers reported the global temperature of Earth has reached a high point not seen in thousands of years. It’s been warming at a rate of .36 ° Fahrenheit per decade for the past 30 years. The current global temperature is the warmest of the interglacial period that started about 12,000 years ago. The warming has been stronger in the far north.

Two important changes in environmental conditions are occurring simultaneously: the “hole” in the ozone layer over Antarctica is shrinking and the Arctic Sea ice is melting away. Glaciers are melting at a faster rate all over the globe.

The ozone layer is an area in Earth’s upper atmosphere made of heavy oxygen that protects Earth from harmful ultraviolet (UV) rays emitted by the sun. UV rays can cause skin cancer and cataracts in humans and harm other animals and plants. The “hole” in the ozone is an area that gets depleted of ozone, letting UV rays through to Earth’s surface. The largest “hole” ever recorded was on September 10, 2000 when it covered 11.5 million square miles. The rate of ozone depletion has slowed down with the passing of international laws restricting the manufacture and use of human-made, ozone-depleting compounds like chlorofluorocarbons and halons. Chlorine and bromine chemicals cause ozone loss, but extremely cold temperatures are a key factor too. Scientists believe the ozone “hole” could disappear completely in 50 years.

Arctic Sea ice is perennial, or year-round. It’s normally about 10 or more feet thick and covers an area about the size of Texas, totaling 280,000 square miles. For 4 years the ice has been shrinking. Between 2004 and 2005, the perennial ice rapidly shrank by 14%. In the East Arctic Ocean, because some of the ice moved by winds to the West Arctic Ocean, the ice shrank nearly 50%. The new ice is only 1 to 7 feet thick, which is much more vulnerable to summer melt-off. If the ice continues to decline, the surrounding ocean will get warmer, accelerating the summer melts and slowing the fall freezes. If all the ice melts off in summer, a vast area would open up and have profound, long-term impacts on the environment.