(DISCLAIMER: “I am not a climate scientist” but I’m trying to process the information anyway, instead of running away from it. That said, there may be errors or inconsistencies in this material that I am not aware of. Use this information at your own risk, and double-check my references to see if you agree with them. Please report any/all such concerns to me ASAP for that I can make adjustments as necessary. Thank you! Mark Dixon, firstname.lastname@example.org)
This is a summary of key temperatures and trends relevant to the UNFCCC COP21 Climate Change Conference in Paris, to be held during the first two weeks of December, 2015. This is a major international gathering sponsored by the United Nations to address climate change with meaningful, binding climate commitments by the global community. It is my hope that this graphical summary will provide important context for decision making at the local, national, and global level, not to mention inspire citizens to take action in support of Dr. James Hansen’s 1°C limit (see below) that we are already expecting to exceed this century. Please find detailed descriptions of the source material for all temperature points below. If you feel overwhelmed by the information, please know that there is so much you can do to help turn the tide! My favorite recommendation is to get organized with other activists and lobby Congress for a strong agreement at COP21 in Paris this December. I also know and respect the methods of the Citizens Climate Lobby and recommend joining if you’re so inclined: http://citizensclimatelobby.org/ . Another noteworthy climate activism organization worth joining is 350.org, with local branches all around the world. And, of course, you can help me fund my own travels and activism via my GoFundMe campaign — particularly if you’d like to see more of these summaries!
Mark’s Quick Assessment: We need to stop emitting CO2 and other greenhouse gasses into the atmosphere as soon as humanly possible and then update our global agricultural and forestry practices to being removing CO2 from the atmosphere ASAP.
Ok, now for a thorough explanation of the diagram:
Business as Usual: 3.9°C (range from 2.9°C to 5.2°C) warming above pre-industrial levels by 2100 assuming current trends on greenhouse gas emissions continue, according to estimates made by Climate Action Tracker. Details at http://climateactiontracker.org/, ©Ecofys and Climate Analytics. (I believe that the Climate Action Tracker is a *great* resource!)
Pledges to UN (INDC’s): An INDC is an “Intended Nationally Determined Contributions,” basically a pledge by a country to reduce its emissions by a certain amount. The online “Climate Action Tracker” (CAT) website has compiled detailed information and ratings for each nation’s INDC, and also compiled all INDC’s into an aggregate assessment regarding impact to the climate through 2100. CAT estimates warming of 3.1°C (range from 2.5°C to 3.8°C) above pre-industrial levels by 2100 based on current INDC pledges. Details at http://climateactiontracker.org/, ©Ecofys and Climate Analytics. Climate Action Tracker is, according to their website, “an independent scientific analysis produced by four research organisations tracking climate action and global efforts towards the globally agreed aim of holding warming below 2°C…”
UN Target (2°C): The most commonly referenced target for a limit on global warming above pre-industrial levels for the purpose of international climate negotiations at the UNFCCC Conferences of Parties (COP). A goal of 1.5°C to 2°C global average temperature above pre-industrial levels was proposed at the 2014 COP20 event in Lima, Peru. According to CarbonBrief.org, we have only 20.9 years of current emissions remaining if we wish to have a 66% chance of keeping global average warming below 2°C. If we seek only a 50% chance of staying below 2°C then we have 28.4 years of current emissions remaining. See additional temperatures and probabilities here: http://www.carbonbrief.org/media/351851/carboncountdown3nologo_575x719.jpg . After settling upon a 2°C limit at the 2010 UNFCC COP, it became evident that 1.5 might be a safer target, particularly considering late-breaking climate news. And so the 1.5°C “stretch goal” (my words there) came into being…
UN Stretch Goal (1.5°C): A “stretch goal” for limiting global warming above pre-industrial levels to 1.5°C, established at the 2014 COP20 event in Lima, Peru. A great many experts convened by the United Nations determined that 2°C was not a safe limit. You can read more about that discussion here: http://www.newrepublic.com/article/121907/limiting-global-warming-2-degrees-celsius-wont-save-us . According to CarbonBrief.org, we have only 6 years of current emissions remaining if we wish to have a 66% chance of keeping global average warming below 1.5°C. If we seek only a 50% chance of staying below 1.5°C then we have 9.8 years of current emissions remaining. See additional temperatures and probabilities here: http://www.carbonbrief.org/media/351851/carboncountdown3nologo_575x719.jpg .
James Hansen Safe Limit: Dr. James Hansen et al. produced a paper (http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0081648) that concludes any global average temperature greater than 1°C (possibly peaking briefly at 1.1 or 1.2°C) over pre-industrial levels may trigger climate feedback mechanisms that take the global temperature to dangerously high levels. This view challenges the 2009 “Copenhagen Accord” generated at COP15 that declares 2°C is a worthwhile limit. From the Hansen paper abstract, “Cumulative emissions of ~1000 GtC, sometimes associated with 2°C global warming, would spur “slow” feedbacks and eventual warming of 3–4°C with disastrous consequences.” And “Continuation of high fossil fuel emissions, given current knowledge of the consequences, would be an act of extraordinary witting intergenerational injustice.” And concludes, “Responsible policymaking requires a rising price on carbon emissions that would preclude emissions from most remaining coal and unconventional fossil fuels and phase down emissions from conventional fossil fuels.” And the paper summarizes the 1°C target with, “Warming of 1°C relative to 1880–1920 keeps global temperature close to the Holocene range, but warming of 2°C, to at least the Eemian level, could cause major dislocations for civilization.”
Current Projection for 2100: 2.2°C (range of 1.3°C to 3.9°C) by 2100 assuming no new greenhouse gas emissions and no GHG sequestration/removal from the atmosphere. This information was derived from a paper shared on the PNAS.org website (Proceedings of the National Academy of Sciences of the United States of America) “On avoiding dangerous anthropogenic interference with the climate system: Formidable challenges ahead,” edited by William C. Clark, http://www.pnas.org/content/105/38/14245.full . The paper gives projections for total committed warming from existing greenhouse gasses in the atmosphere and indicates that “About 90% or more of the rest of the committed warming of 1.6°C will unfold during the 21st century”. I reduced the range of 1.4°C to 4.3°C by 10% to approximate the shorter time horizon (yielding a new range of 1.3°C to 3.9°C). As with the next item (current projection for 2055) this is a VERY ROUGH approximation and makes inferences about data that would probably not hold up to academic scrutiny, but can be useful for illustrating how we are not currently feeling the full impacts of greenhouse gasses that have already been emitted, and will not for many years.
Current Projection for 2055: 1.45°C warming likely by 2055 assuming no new greenhouse gas emissions and no GHG sequestration/removal from the atmosphere. This accounts for a “thermal lag” time of between 25 and 50 years (rounded to 40 for simplicity, as proposed at http://www.skepticalscience.com/Climate-Change-The-40-Year-Delay-Between-Cause-and-Effect.html ) that it takes for the current greenhouse gas composition in the atmosphere to have the bulk of its impact on the global temperature. Assumes .6°C of warming remaining to emerge from the current global average, pulled from a 2005 assessment by Dr. James Hansen et al. http://www.sciencemag.org/content/308/5727/1431.abstract . This is a VERY ROUGH approximation and connects some different data sources that may not be well suited for combining, but I wanted to illustrate how we are not currently feeling the full impacts of greenhouse gasses that have already been emitted, and will not for many years. So if we think the weather is weird now, hold onto your hats while we march into the future and realize the full consequences of yesterday’s emissions.
Currently Experiencing: Current estimates per Wikipedia indicate “global average (land and ocean) surface temperature shows a warming of 0.85 [0.65 to 1.06] °C in the period 1880 to 2012” https://en.wikipedia.org/wiki/Global_warming.