The graph below shows the projected increase in global average temperature above 1850 levels for four different greenhouse gas (GHG) emissions scenarios.
- The red line labeled “business as usual” uses Representation Concentration Pathway (RCP) 8.5 emissions projections from the IPCC Fifth Assessment.
- The orange line labeled “renewable electricity” results from cutting emissions 25% between 2020 and 2040 to represent 100% renewable electricity by 2040. World and Colorado emissions from electric power generation are both approximately 25% of the total.
- The light green line labeled “90% x 2050” results from cutting emissions 90% below 2005 levels by 2050, starting in 2020. This scenario corresponds to the current version of HB19-1261.
- The dark green line labeled “recommended” results from cutting emissions 100% below 2005 levels by 2035, starting in 2020. The Colorado Coalition for a Livable Climate recommends setting goals for making emissions cuts between 2020 and 2030 that put Colorado on this path to net zero emissions.
- The tan box shows the 1.5° C – 2.0° C range of “dangerous interference with the climate system” as defined by the U.N Framework Convention on Climate Change.
Conclusion: Only the cuts recommended by the Colorado Coalition for a Livable Climate – extended worldwide – would be likely to prevent dangerous interference with the climate system.
Projections use a simple calculator that mixes CO2 emissions into the air and removes a fraction by plant growth and ocean uptake. It then calculates warming over time using a method that closely matches the average projected in the IPCC Fifth Assessment Report. Details are available at http://biocycle.atmos.colostate.edu/shiny/FCSG.