Arguments
Software
Resources
Comments
The Consensus Project
Translations
About
Support
Latest Posts
- Skeptical Science New Research for Week #47 2024
- Durability of carbon dioxide removal is critical for stabilizing temperatures
- Sabin 33 #3 - Solar panels generate too much waste and will overwhelm landfills
- Here’s how governments could fix their Paris climate commitment failures
- 2024 SkS Weekly Climate Change & Global Warming News Roundup #46
- Skeptical Science New Research for Week #46 2024
- 20 fact briefs published in collaboration with Gigafact!
- Sabin 33 #2 - Are toxic heavy metals from solar panels posing a threat to human health?
- 2024 will be the first year above 1.5°C
- 2024 SkS Weekly Climate Change & Global Warming News Roundup #45
- Fact brief - Is there an expert consensus on human-caused global warming?
- Skeptical Science New Research for Week #45 2024
- The planet is ‘on the brink of an irreversible climate disaster,’ scientists warn
- Sabin 33 #1 - Are electromagnetic fields from solar farms harmful to human health?
- Volunteer activity: Evaluate automated climate misinformation debunkings
- 2024 SkS Weekly Climate Change & Global Warming News Roundup #44
- Fact brief - Are most glaciers growing?
- Rebutting 33 False Claims About Solar, Wind, and Electric Vehicles thanks to the Sabin Center for Climate Change Law
- Skeptical Science New Research for Week #44 2024
- The hidden health toll of hurricanes
- Climate Adam: Is climate change fuelling mega hurricanes?
- Jobs in wind, solar, and energy storage are booming. Is your state keeping up?
- 2024 SkS Weekly Climate Change & Global Warming News Roundup #43
- Fact brief - Do volcanoes emit more CO2 than humans?
- Skeptical Science New Research for Week #43 2024
- Why widening highways doesn’t reduce traffic congestion
- Climate Risk
- Welcome to the world of personal air conditioning
- 2024 SkS Weekly Climate Change & Global Warming News Roundup #42
- Skeptical Science New Research for Week #42 2024
Archived Rebuttal
This is the archived Intermediate rebuttal to the climate myth "IPCC overestimate temperature rise". Click here to view the latest rebuttal.
What the science says...
|
The IPCC surface temperature projections have been extremely accurate thus far. |
1990 IPCC FAR
The Intergovernmental Panel on Climate Change (IPCC) First Assessment Report (FAR)was published in 1990. The FAR used simple global climate models to estimate changes in the global-mean surface air temperature under various CO2 emissions scenarios. Details about the climate models used by the IPCC are provided in Chapter 6.6 of the report.
The IPCC FAR ran simulations using various emissions scenarios and climate models. The emissions scenarios included business as usual (BAU) and three other scenarios (B, C, D) in which global human greenhouse gas emissions began slowing in the year 2000. The FAR's projected BAU greenhouse gas (GHG) radiative forcing (global heat imbalance) in 2010 was approximately 3.5 Watts per square meter (W/m2). In the B, C, D scenarios, the projected 2011 forcing was nearly 3 W/m2. The actual GHG radiative forcing in 2011 was approximately 2.8 W/m2, so to this point, we're actually closer to the IPCC FAR's lower emissions scenarios.
The IPCC FAR ran simulations using models with climate sensitivities (the total amount of global surface warming in response to a doubling of atmospheric CO2, including amplifying and dampening feedbacks) of 1.5°C (low), 2.5°C (best), and 4.5°C (high) for doubled CO2 (Figure 1).
Figure 1: IPCC FAR projected global warming in the BAU emissions scenario using climate models with equilibrium climate sensitivities of 1.5°C (low), 2.5°C (best), and 4.5°C (high) for doubled atmospheric CO2
Figure 2 accounts for the lower observed global heat imbalance than in the IPCC BAU projection, and compares its 'Best' adjusted projection with the observed global surface warming since 1990.
Figure 2: IPCC FAR BAU global surface temperature projection adjusted to reflect observed GHG radiative forcings 1990-2011 (blue) vs. observed surface temperature changes (average of GISS, NCDC, and HadCRUT4; red).
Scorecard
The IPCC FAR 'Best' BAU projected rate of warming was 0.25°C per decade. However, that was based on a scenario with higher emissions than actually occurred. When accounting for actual GHG emissions, the IPCC average 'Best' model projection of 0.2°C per decade is within the uncertainty range of the observed rate of warming (0.15 ± 0.08°C) per decade since 1990.
1995 IPCC SAR
The IPCC Second Assessment Report (SAR)was published in 1995, and improved on the FAR by estimating the cooling effects of aerosols — particulates which block sunlight. The SAR included various human GHG emissions scenarios, so far its scenarios IS92a and b have been closest to actual emissions.
The SAR also maintained the "best estimate" equilibrium climate sensitivity used in the FAR of 2.5°C for a doubling of atmospheric CO2. Using that sensitivity, and the various IS92 emissions scenarios, the SAR projected the future average global surface temperature change to 2100 (Figure 3).
Figure 3: Projected global mean surface temperature changes from 1990 to 2100 for the full set of IS92 emission scenarios. A climate sensitivity of 2.5°C is assumed.
Figure 4 compares the IPCC SAR global surface warming projection for the most accurate emissions scenario (IS92a) to the observed surface warming from 1990 to 2012.
Figure 4: IPCC SAR Scenario IS92a global surface temperature projection (blue) vs. observed surface temperature changes (average of GISS, NCDC, and HadCRUT4; red).
Scorecard
The IPCC SAR IS92a projected rate of warming was
0.25°C per decade. However, that was based on a scenario with higher emissions than actually occurred. When accounting for actual GHG emissions, the IPCC average 'Best' model projection of 0.2°C per decade is within the uncertainty range of the observed rate of warming (0.15 ± 0.08°C) per decade since 1990.
Updated on 2012-12-23 by dana1981.
THE ESCALATOR
(free to republish)