We also know a lot about Earth temperature changes . “Global temperature changes naturally all of the time, in both directions and at many scales of intensity .“The warmest year in the U.S. in the last century was 1934, not 1998. The U.S. has the best and most extensive temperature records in the world . “Global temperature peaked in 1998 on the current 60-80 year cycle, and has been episodically declining ever since. This cooling absolutely falsifies claims that human carbon dioxide emissions are a controlling factor in Earth temperature . “Voluminous historic records demonstrate the Medieval Climate Optimum (MCO) was real and that the “hockey stick” graphic that attempted to deny that fact was at best bad science. “The MCO was considerably warmer than the end of the 20th century . “During the last 100 years, temperature has both risen and fallen, including the present cooling. All the changes in temperature of the last 100 years are in normal historic ranges, both in absolute value and, most importantly, rate of change.