Houghton also believes that global warming will accelerate the spread of many diseases from the tropics to the temperate world, oftentimes spread by insects that thrive in warm climates. Anecdotal evidence of global warming is available to any casual reader. Ice core records, for example, indicate that average temperatures on higher mountains in the tropics are higher than they have been in 2,000to 3,000 years. A piece of the Antarctic ice sheet the size of Rhode Island slid into the sea during 1995. Average temperatures in some areas of Antarctica have risen 4 to 5 degrees Celsius during the last fifty years.
Tests indicate that arctic ice also is thinning at an alarmingly fast rate in geological time.
Sea levels around the world have risen an average of four to ten inches during the last century, an amount that may seem small until one looks at it in terms of geologic time. The seas are rising faster than they have since the end of the last ice age, and stand at their highest level in 5,000 years. Not only are summers getting warmer on average, but humidity levels also are rising, making hot days and nights seem even more miserable. They found that the level of humidity is rising even more quickly than the temperature itself, especially during night-time hours. Houghton's book should be read in detail by anyone who still believes that global warming is a matter of whether or not.