Adjust the sliders on the left to cut emissions separately for rich and poor countries. Specify when cuts should begin, how deep they will be, and when emissions will stabilize at a lower level. Try to avoid dangerous interference with the climate system!
Carbon emissions to the atmosphere are derived from historical data (mostly national-level inventories) and from scenarios developed for use in the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment. Projected future emission scenarios are called “Representative Concentration Pathways” (RCP). These use integrated assessment models that combine regional analyses of economics, policy, energy, and climate to create scenarios of future emissions from fossil fuel combustion and changing land use.
Decadal estimates of fossil fuel combustion and land use emissions are downloaded from the IPCC RCP database, combined with historial data, and interpolated to annual values for 250 years from 1850-2100. For this web calculator, baseline emissions represent a “business as usual” scenario under which “no policy” is assumed to reduce future emissions. This is the “RCP 8.5” scenario used by IPCC AR5 so named because it leads to about 8.5 Watts of extra heat radiation for each square meter of the planet when CO2 concentrations peak around the year 2150.
You can read all about the IPCC RCP scenarios here.
The user is invited to specify separate cuts to future emissions in the “rich countries” (developed world) and the “poor countries” (developing world). Only emissions from fossil fuel combustion are adjustable: future emissions due to deforestation (land use) are applied according to the IPCC RCP8.5 scenario without any adjustment.
The “rich countries” include the OECD 90 countries: Western Europe (Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, Turkey, United Kingdom), Northern America (Canada, United States of America) and Pacific OECD (Australia, Fiji, French Polynesia, Guam, Japan, New Caledonia, New Zealand, Samoa, Solomon Islands, Vanuatu). The “poor countries” are considered to be everywhere else (non-OECD).
Users specify a year for cuts to begin in each region (the baseline year), a year by which to meet a specified target, and a percentage reduction below the baseline. Emissions in each region are then ramped down beginning in the baseline year and follow a linear ramp until the target year. After the reduction period ends, emissions are assumed to remain constant, so even a zero percent cut will result in lower emissions than the “business as usual” scenario in which emissions continue to rise.
Quantitative comparisons of emissions to any baseline year can be made by clicking on the “Climate” tab to the right to see a table of the numbers used to make the graphs,
Starting from an atmospheric CO_2 concentration in 1850 (derived from snow and ice samples), each year's value is updated by adding emissions and subtracting “sinks” due to absorption of excess CO2 by the oceans and by plants and soils on land. The basic arithmetic can be summarized as follows:
CO2(new) = CO2(old) + (emissions - sinks) / (mass of the atmosphere)
Emissions are prescribed from the RCP 8.5 scenario after applying user-specified cuts as described above. Emissions from both fossil fuel combustion and land use (deforestation) contribute to changes in CO2.
Sinks are more complicated. Most people are familiar with the idea that burning fuels made of carbon adds CO2 to the atmosphere. But many people are unaware that about half of the CO2 added each year by fossil fuel combustion is removed by absorption into the oceans and the land.
This web tool uses a simple global model of sinks consisting of six boxes: one for the atmosphere, two for the oceans, and three for the land. Ocean uptake is calculated using the chemistry of CO2 dissolving into seawater and the physical mixing between the surface and deep oceans. Uptake of CO2 on land is driven by fertilization of plants by both CO2 and nitrogen, by longer growing seasons in the far north, and by regrowth of forests in the developed world that were deforested in the 18th and 19th Centuries. Carbon is also released from soils as climate change warms them.
Global average warming is assumed to be 3 degrees Celsius for each doubling of atmospheric CO2, which is consistent with past climate variations over centuries, millennia, and eons as well as with climate models used by the IPCC. Warming is assumed to be delayed by 20 years relative to changes in CO2, mainly because of the heat capacity of oceans. You can explore the sensitivity of climate to CO2 using the online Earth[carbon] model.
The United Nations Framework Convention on Climate Change (UN FCCC) adopted as a central objective the stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. This has been widely assumed to mean limiting global average warming to 2 degrees Celsius. In 2010, the 195 governments that are parties to the UN FCCC formally adopted the 2 degree definition of this objective. Serious consequences may well happen before the global average temperature warms by 2 degrees Celsius, but since this threshold is widely used and has formal legal status in climate negotiations, it's indicated as a dashed line on the climate graphs here.
Readers in the USA are more familiar with temperatures in Fahrenheit than Celsius, so the web tool has the option to instead calculate warming in Fahrenheit (1 degree Celsius = 1.8 degrees Fahrenheit). Also, continental regions like the central USA warm much faster than the global average, because most of the world is covered by deep oceans and ice that warm very slowly. Users can therefore choose to report warming for the middle of the USA instead of the global average. Mid-USA warming is assumed to be 1.6 times more than the global mean, based on IPCC climate scenarios.
This calculator is part of a series of simple models of the Earth System developed by
Scott Denning, Professor of Atmospheric Science, CMMAP, Colorado State University
See many more at my web site
This video was produced by the Fort Collins Sustainability Group.