Natural variability can explain much of Earth's average temperature variation since the end of the last ice age, but over the past century, global average temperature has risen from near the coldest to the warmest levels in the past 11,300 years.
Ocean waves slowly eat away coastal cliffs the world over, but in parts of Alaska, these processes have accelerated due to changing climate. These photos document a cliff collapse near Drew Point in the late 2000s.
How much sunlight Earth reflects naturally varies a lot. The bigger the range of natural variability, the greater the odds that any evidence of a manmade effort to brighten up the planet would be lost in the “background noise.”
Most of the Arctic boundary waters were warmer than average in summer 2013, but a few cool pockets appeared in the western Arctic and the Greenland Sea. Warmer waters are drawing new species from lower latitudes into the Arctic.