Increase in Global Temperature for Four Different Emissions Scenarios

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.

Temperature Graph rev2

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.

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