CO2 and Climate Calculator with Emission Controls

Emissions

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 in the year 2100.

You can read all about the IPCC RCP scenarios here.

Emissions Reductions

The user is invited to specify a period of years to undertake emission reductions and a total percentage by which emissions will be reduced over that period. After the reduction period ends, emissions are assumed to remain constant at the reduced level, so even a zero percent cut will result in lower emissions than the “business as usual” scenario in which emissions continue to rise. For reference, the program also displays the total emission reduction relative to a comparison year chosen by the user.

The graphs on the right side of the window show the “business as usual” scenario in red and the result of reduced emissions in green. The top panel shows global CO2 emissions. The middle panel compares the resulting CO2 in the atmosphere for each scenari. The bottom panel shows climate warming either for the global average or for the central USA if that option is chosen. Warming is greater for inland areas than oceans and coasts because of the enormous heat capacity of the oceans.

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,

Atmospheric CO2

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.

To learn more about the simplified model of carbon sources and sinks please see the EarthCarbon model online or download the Earth[Carbon] app for iPad.

Climate

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. In 2015, the countries further agreed to try to limit warming to 1.5 degrees Celsius, so the graph shows the range of 1.5 to 2 degrees as the threshold for “Dangerous interference.”

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