Oceans and climate science: Higher water mark

TIDES ebb and flow but mean sea levels are among the constants of climate science. Though things like the recent slowdown in the rise of average surface temperatures are puzzling, scientists can at least point to higher sea levels as clear evidence that climate change is real. The rise is caused by thermal expansion (hot water expands) and by melting ice sheets. And the facts are observable: thousands of gauges--such as that pictured above--measure tides around the world, with some records going...