Many people may be wondering, “what the heck is going on in climate science,” and, for that matter, “what the heck is happening to our climate?” On the one hand, reports from U.S. government agencies indicate that 2017 was the 3rd warmest year on record, 1.5 degrees (Fahrenheit) above the average temperature of the 20th century, and that the 6 warmest years on record have all occurred since 2010. But, in their commentary in February 8’s N&O, Tim Ball and Tom Harris claim the reported warming cannot be detected from available data.
Who is right?, how do we know? and what does it mean for the future?
As it turns out, there is good reason to believe that temperature analyses published by science agencies in the U.S. and around the world are accurate. The data are carefully controlled for errors and biases, and the warming they show aligns closely with what is happening elsewhere on Earth. Among many such indicators glaciers are melting, Arctic sea ice and snow cover are retreating, the atmosphere above the ground is warming, ice sheets – in Greenland and the Antarctic are shrinking, and ocean temperatures and sea level are rising.
These are independent measures of the climate, and they all point to a warming world. For example, ocean observations beneath the surface, taken in oceanographic surveys and, more recently by thousands of autonomous (robot) floats, show a steady rise in the heat content of the oceans. Sea water expands when it warms, so a warming ocean takes up more space, and sea level rises. This is confirmed by careful analyses of tide-gauge records from all over the world, another independent source of data.
And the warming is no surprise. It arises from the basic physics, well known for over a hundred years, of how infrared (heat) radiation interacts with the heat-trapping gases we are adding to the atmosphere.
Does it matter that Earth is warming? After all, one-and-a-half degrees doesn’t sound like much, since temperatures in Raleigh often swing ten times that much in a single day. But the pace and global scope of the current warming is, as far as we can tell, unprecedented in the 10,000 years during which we humans have built our civilization. This warming is causing more frequent and more severe heat waves, rising seas that exacerbate coastal floods, prolonged wildfire seasons, and heavier rains within storms. These are common-sense consequences of a warmer world: the hottest days get hotter, melting ice and expanding oceans raise sea level, and forests become more vulnerable to fire as the winter season of snow cover gets shorter and summertime evaporation increases. Because there is greater humidity in a warmer atmosphere, the strongest rains intensify, with consequent increases in flooding.
For the future, we can say with confidence that if emissions of heat-trapping gases continue unabated, global warming will continue and will accelerate, and the impacts of warming, the same impacts we are experiencing now, will get worse. Consider, for example, the millions of people living in low-lying areas all over the world who will become climate refugees if sea level rises, as is expected, at a faster and faster rate.
But the most dire consequences of climate change are not inevitable. The greatest uncertainty in projecting future climate, uncertainty that no amount of climate science and computer modeling can eliminate, comes from what we will do. Every ton of carbon dioxide released into the atmosphere, from burning coal, oil and natural gas, and from clearing forests, makes global warming and its impacts worse, but this means that every ton of carbon we do not release, because we choose renewable sources for our energy, or use energy more efficiently, or or stop destroying forests, makes the problem of global warming less severe. While some continued warming is inescapable, we can choose how much heat trapping gases we release into the atmosphere.
In so doing, we choose what happens to our climate and we chose what sort of planet with bequeath to our children. These are choices that must be made using real science and real data. Pretending the science and the data don’t exist cannot absolve us of our responsibility to take prompt sound action and to meet our obligation to leave to our children and grandchildren a planet on which they can thrive.
Walter Robinson, professor of atmospheric sciences at NC State University, is a climate scientist. Lisa Falk is a geologist and teaches courses in Earth-system science at NC State. Justin Baumann is a doctoral student in marine sciences at the University of North Carolina Chapel Hill, who studies coral reefs.