The God Species_ How the Planet Can Survive the Age of Humans - Mark Lynas [28]
Never mind the enduring global-warming controversies in the media; these are a distraction. The climate change planetary boundary is the one that is best understood and that we know most about how to achieve. Moreover, meeting the boundary is a basic requirement for any level of sustainable planetary management: If CO2 continues to rise, and temperatures begin to race out of control, then the biodiversity boundary, the ozone boundary, the freshwater boundary, the land use boundary, and ocean acidification boundaries cannot be met either, and the remaining planetary boundaries are also called into question.
The climate boundary is humanity’s first and biggest test that will reveal early on whether we are truly capable of managing our environmental impacts in a way that protects the capacity of the biosphere to continue to operate as a self-regulating system. It is a testament to our intelligence that we have developed our scientific understanding so far that we now know a great deal about how the climate system works and can define with some confidence where the planetary boundary should lie. It is perhaps testament to our stupidity, however, that despite decades of research and advocacy on climate, all pointing at the need to control greenhouse gas production, human emissions today continue inexorably to rise.
Thankfully the technologies and strategies that humanity needs to achieve the climate boundary are today no mystery. We have all the tools necessary to begin a wide-scale decarbonization of the global economy and to achieve this at the same time as both living standards and population numbers are rising rapidly in the developing world. But environmentalism will need to change at the same time. Much of what environmentalists are calling for will either not help much or is actually thwarting progress toward solving climate change. It is time for a new—and far more pragmatic—approach that does not hold climate change hostage to a rigid ideology.
350: CURRENT EVIDENCE
First we need to establish whether 350 is actually the right number and one that is supported by science. There are three broad lines of evidence that support the conclusion that atmospheric CO2 concentrations need to be limited to 350 ppm. The first is the sheer rapidity of changes already under way in the Earth system, changes I never dreamed I would see so quickly when I started working on this subject more than ten years ago. These warn of looming danger. The second is modeling work suggesting that positive feedbacks—or thresholds, or tipping points, call them what you like—are getting perilously close. The third, and perhaps most conclusive, is evidence from the distant past linking temperatures with carbon dioxide concentrations in earlier geological epochs.
The best place to look for confirmation that our planet is gaining heat is not the air temperature at the ground, but the energy imbalance—the difference between incoming and outgoing radiation—at the very top of the atmosphere. There our sentinel machines, the satellites silently orbiting the planet 24 hours a day, show clearly that outgoing longwave heat radiation is increasingly being trapped at exactly those parts of the spectrum that correspond with the different greenhouse gases building up in the atmosphere below.1 Natural variability is important in determining the average temperature each year, but recent records are revealing: The hottest year on record, according to NASA, is now tied between 2010 and 2005, with 2007 and 2009 statistically tied for second and third hottest.2 Whatever the individual temperature records, the climatic baseline is visibly shifting: Every year in the