Warming caused by cumulative carbon emissions towards the trillionth tonne

Abstract

Global efforts to mitigate climate change are guided by projections of future temperatures. But the eventual equilibrium global mean temperature associated with a given stabilization level of atmospheric greenhouse gas concentrations remains uncertain, complicating the setting of stabilization targets to avoid potentially dangerous levels of global warming. Similar problems apply to the carbon cycle: observations currently provide only a weak constraint on the response to future emissions. Here we use ensemble simulations of simple climate-carbon-cycle models constrained by observations and projections from more comprehensive models to simulate the temperature response to a broad range of carbon dioxide emission pathways. We find that the peak warming caused by a given cumulative carbon dioxide emission is better constrained than the warming response to a stabilization scenario. Furthermore, the relationship between cumulative emissions and peak warming is remarkably insensitive to the emission pathway (timing of emissions or peak emission rate). Hence policy targets based on limiting cumulative emissions of carbon dioxide are likely to be more robust to scientific uncertainty than emission-rate or concentration targets. Total anthropogenic emissions of one trillion tonnes of carbon (3.67 trillion tonnes of CO(2)), about half of which has already been emitted since industrialization began, results in a most likely peak carbon-dioxide-induced warming of 2 degrees C above pre-industrial temperatures, with a 5-95% confidence interval of 1.3-3.9 degrees C.

Switch: A Planning Tool for Power Systems with Large Shares of Intermittent Renewable Energy

“…The cost of delivering power is divided into five components: (1) the capital cost of building power plants, (2) operations and maintenance (O&M) costs incurred each year at active power plants, (3) variable O&M costs incurred for each megawatt-hour of electricity produced by each plant, (4) the cost of any fuel used to generate electricity, and (5) a "carbon cost" applied to each metric ton of carbon dioxide emitted by a power plant. 2 For transmission capacity, only a capital cost and annual fixed O&M cost are considered.…”

“…2 For transmission capacity, only a capital cost and annual fixed O&M cost are considered. The cost of building and maintaining local transmission and distribution infrastructure is represented by a simple annual payment that must be made to finance and maintain each megawatt of capacity in each zone.…”

“…1 The best estimate is that this will require limiting cumulative CO 2 emissions to about 10 12 tonnes of carbon before fossil fuels are completely phased out. 2 However, it is possible that the safe emissions budget is as low as half this levelapproximately the amount we have already emitted. 3 Achieving deep emission reductions early in the century will increase the chance of achieving the 2°C target, and/or raise the emission budget available later in the century.…”

The Impact of First-Generation Biofuels on the Depletion of the Global Phosphorus Reserve

“…However, very high increases in the efficiency of P use are required to balance P depletion and climate change mitigation impacts, ranging from 31% for sugarcane to 89% for wheat and rapeseed, in case of a 3°C temperature increase threshold and the perhaps optimistic estimate of global P reserves (65 thousand million ton rock phosphate) of Jasinski (2011). There are substantial uncertainties in our analysis, which relate to the global P reserves, the CO 2 that can be emitted while avoiding certain levels of climate change (compare Matthews et al 2009;Meinshausen et al 2009;Allen et al 2009) and the relative impacts of depleting P reserves versus climate change. Also, we attributed P to biofuel feedstock versus co-products on the basis of their relative economic value, even though this does not necessarily represent the distribution of P over these products.…”

“…Based on Matthews et al (2009), we assume that the CO 2 emissions from 2009 onward need to be restricted to a best estimate of 2.9 tT CO 2 in order to avoid a 2°C temperature increase. Allen et al (2009) indicate most likely maximum emissions of 5.9 and 11.0 tT CO 2 required to restrict global temperature increase from 3 to 4°C, respectively.…”