Climate change and trace gases

Abstract

Palaeoclimate data show that the Earth's climate is remarkably sensitive to global forcings. Positive feedbacks predominate. This allows the entire planet to be whipsawed between climate states. One feedback, the 'albedo flip' property of ice/water, provides a powerful trigger mechanism. A climate forcing that 'flips' the albedo of a sufficient portion of an ice sheet can spark a cataclysm. Inertia of ice sheet and ocean provides only moderate delay to ice sheet disintegration and a burst of added global warming. Recent greenhouse gas (GHG) emissions place the Earth perilously close to dramatic climate change that could run out of our control, with great dangers for humans and other creatures. Carbon dioxide (CO 2 ) is the largest human-made climate forcing, but other trace constituents are also important. Only intense simultaneous efforts to slow CO 2 emissions and reduce non-CO 2 forcings can keep climate within or near the range of the past million years. The most important of the non-CO 2 forcings is methane (CH 4 ), as it causes the second largest human-made GHG climate forcing and is the principal cause of increased tropospheric ozone (O 3 ), which is the third largest GHG forcing. Nitrous oxide (N 2 O) should also be a focus of climate mitigation efforts. Black carbon ('black soot') has a high global warming potential (approx. 2000, 500 and 200 for 20, 100 and 500 years, respectively) and deserves greater attention. Some forcings are especially effective at high latitudes, so concerted efforts to reduce their emissions could preserve Arctic ice, while also having major benefits for human health, agricultural productivity and the global environment.

Improved global simulations of gross primary product based on a new definition of water stress factor and a separate treatment of C3 and C4 plants

“…It had the warmest decades in the instrumental record and a significant increase in atmospheric CO 2 levels (Houghton et al, 2001;Hansen et al, 2007). Terrestrial ecosystems, including both vegetation and soil carbon pools, play an important role in the carbon cycle between land and atmosphere through photosynthesis and respiration.…”

Differences between the last two glacial maxima and implications for ice-sheet, δ18O, and sea-level reconstructions

“…First, temporal changes in the radiative balance of climate are important because ice masses have high albedo and reflect incoming solar radiation (e.g., Hansen et al, 2007Hansen et al, , 2008K€ ohler et al, 2010, 2015Rohling et al, 2012;PALAEOSENS project members, 2012;Martínez-Botí et al, 2015;Friedrich et al, 2016). Second, temporal development of ice-age cycles provides critical information about the nature of long-term climate cooling over the past few million years, in response to CO 2 reduction and interactions among ice, land cover, and climate (e.g., Clark et al, 2006;K€ ohler and Bintanja, 2008;de Boer et al, 2010de Boer et al, , 2012Hansen et al, 2013).…”

Restore: An R of sustainability that can tame the “conundrum”

“…Balancing the rebound effect does not depend on knowledge of the CO 2 intensity of the involved items (equation 22), thus simplifying a practical implementation. Eigth, the approach presented here represents a "future-proofing" of sustainability efforts for a scenario in which removal of greenhouse gases from the atmosphere may become a necessity [25,24] and for a scenario in which rebound effects are even more prevalent than today [12]. Ninth, a main driving force for conservation efforts are financial savings.…”