What environmental conditions must exist for earth's climate system to stabilize?  CO2.earth presents a few basic concepts for understanding climate stabilization in an earth systems context.  Consider the links here at Step 3 a possible starting place.  It is far from comprehensive or finished.

What environmental conditions must exist for earth's climate system to stabilize?  CO2.earth presents a few basic concepts for understanding climate stabilization in an earth systems context.  Consider the links here at Step 3 a possible starting place.  It is far from comprehensive or finished.

 

GB4L

Global Before Local

 

"We have a clearer picture of future climate changes on a global scale than of the local consequences associated with a global warming.  And we know why."

~ Rasmus E. Benestad 2015 [info]

 

Local data is more variable and potentially at odds with overall global trends.  It can tell us a lot, but global data can signal a planetary trend that can be clearer and more reliable than local signals.

 

RealClimate 2015  Climate change is coming to a place near you

 

 

Stabilization

CO₂ Stabilization Prerequisites

 

Intro

 

The IPCC published a 'Frequently Asked Question' in 2007 that quantifies the changes in atmospheric stabilization for different greenhouse gasess based on the percentage of cuts made in global emissions from human sources.  Based largely on that resource, the relationship between changes in CO2 emissions and changes in atmospheric CO2 is summarized below.

 

Emissions Changes vs. Atmospheric Changes

 

A 10% cut in global CO2 emissions will result in about a 10% cut in the growth rate for atmospheric CO2 concentrations.  To stabilize atmospheric CO2 in either the short or long term, much deeper cuts are needed.

 

"A 50% reduction would stabilise atmospheric CO2, but only for less than a decade. After that, atmospheric CO2 would be expected to rise again as the land and ocean sinks decline owing to well-known chemical and biological adjustments. Complete elimination of CO2 emissions is estimated to lead to a slow decrease in atmospheric CO2 of about 40 ppm over the 21st century."

~ IPCC (2007, p. 824)

 

Short Term Stabilization

 

To understand why emissions need to be cut in half to achieve atmospheric stabilization, you will be learning about the airborne fraction for CO2 emissions from human sources.  See the next tab for an introduction to this concept. 

 

Long Term Stabilization

 

The reference above to "complete elimination of CO2 emissions" is not simply an idealized scenario.  It is a prerequisite for long-term stabilization of CO2 concentrations in the atmosphere.

"Only in the case of essentially complete elimination of emissions can the atmospheric concentration of CO2 ultimately be stabilised at a constant level. All other cases of moderate CO2 emission reductions show increasing concentrations because of the characteristic exchange processes associated with the cycling of carbon in the climate system."

~ IPCC (2007, p. 824)

 

This information is critical for comprehending the level of emissions cuts needed to stabilize atmospheric CO2 and, practically speaking, global temperature and global climate as well.

 

Consequences of Delay

 

The Fifth Assessment report also states that cumulative CO2 emissions over time increase damages and possibilities of irreversible impacts. 

 

"Substantial cuts in GHG emissions over the next few decades can substantially reduce risks of climate change by limiting warming in the second half of the 21st century and beyond. Cumulative emissions of CO2 largely determine global mean surface warming by the late 21st century and beyond. Limiting risks across RFCs would imply a limit for cumulative emissions of CO2. Such a limit would require that global net emissions of CO2 eventually decrease to zero and would constrain annual emissions over the next few decades."

~ IPCC (2014, p. 19)

 

Other GHGs

 

To identify emissions prerequisites for stabilizing other greenhouse gases, see the IPCC's 2007 FAQ 10.3.

 

Takeaway

 

Scientific information about the stabilization of CO2 concentrations point to zero global CO2 emissions from human sources as a prerequisite for achieving and sustaining stabilized atmospheric CO2 levels for the long term. 

 

Discussion

 

Humanity has some choices to make.

One is whether or not it wishes to achieve stabilization.  The signatures of 195 countries adopting the UN Framework Convention on Climate Change, Article 2 in particular, indicates that humanity made that choice in the 1990s.  Our institutions opted to achieve stabilization.

The next choices are these:

1. By what date or atmospheric levels will humanity achieve initial stabilization of CO2 and other GHGs (including a rapid global cut in human CO2 emissions of about 50%)?
   
   
2. By what date or atmospheric levels will humanity achieve long-term stabilization of CO2 and other GHGs (via the elimination of human CO2 emissions).

 

Links

 

IPCC 2007  FAQ 10.3: If GHG emissions reduce, how quickly do atmospheric levels decrease?

Science Daily  Stabilizing climate requires near-zero carbon emissions

Carbon Tracker  Fossil fuels are dead. The rest is just detail.

 

Related Links

 

GRL 2008  Matthews & Caldeira | Stabilizing climate requrieds near-zero emissions [.pdf]

 

Related Concept

 

See the next tab for an introduction to "airborne fraction."

 

References

 

IPCC. (2014). Climate change 2014: Synthesis report. Contribution of working groups I, II and III to the fifth assessment report of the Intergovernmental Panel on Climate Change. (Core Writing Team, R. K. Pachauri, & L. A. Meyer Eds.). Geneva, Switzerland: IPCC. [web + .pdf + Chinese + Korean]

Meehl, G. A., Stocker, T. F., Collins, W. D., Friedlingstein, P., Gaye, A. T., Gregory, J. M., . . . Zhao, Z.-C. (2007). Global climate projections. Frequently asked question 10.3:  If emissions of greenhouse gases are reduced, how quickly do their concentrations in the atmosphere decrease?   In S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K. B. Averyt, M. Tignor, & H. L. Miller (Eds.), Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (pp. 824-825). Cambridge, UK and New York, USA: Cambridge University Press.

 

CO2 AF

CO2 Airborne Fraction

 

Links

 

GCP  2015 global carbon budget highlights (compact)

Science Daily '09  Is the airborne fraction of anthropogenic CO₂ increasing?

SkS   CO₂ levels and airborne fraction

ACS  GHG sources and sinks

SkS  Commentary by John Cook

CO₂.earth  Global carbon emissions

 

Papers

 

ESSD '15  Le Quéré et al. | Global carbon budget 2015 [.pdf]

Biogeosciences '15 Sitch et al. | Recent trends, regional CO2 sources and sinks [.pdf]

GRL  Is the airborne fraction of anthropogenic CO₂ emissions increasing?

Nature Geoscience '09  Le Quéré et al. | Trends in the sources and sinks of CO2 [.pdf via GCP]

 

References

 

Canadell JG et al. (2007) Contributions to accelerating atmospheric CO2 growth from
economic activity, carbon intensity, and efficiency of natural sinks. PNAS 104:
18866–18870, http://www.pnas.org/content/104/47/18866.abstract

Friedlingstein P, Houghton RA, Marland G, Hackler J, Boden TA, Conway TJ,
Canadell JG, Raupach MR, Ciais P, Le Quéré C. Update on CO2 emissions. Nature
Geoscience, Online 21 November 2010.

Le Quéré, C., Moriarty, R., Andrew, R. M., Canadell, J. G., Sitch, S., Korsbakken, J. I., . . . Zeng, N. (2015). Global carbon budget 2015. Earth System Science Data, 7(2), 349-396. doi:10.5194/essd-7-349-2015

Raupach MR et al. (2007) Global and regional drivers of accelerating CO2 emissions.
Proceedings of the National Academy of Sciences 14: 10288-10293.
http://www.pnas.org/content/104/24/10288

 

 

Inertia

Climate Change Inertia

 

Inertia in the climate system means that climate change and climate change impacts will continue for decades to centuries after source factors responsible for the changes are removed.  Three types of inertia affecting the climate system are introduced below, along with the masking effect of aerosols.

This tab considers the following: 

• committed CO2 emissions of existing infrastructure
• committed temperature and sea level increases from GHG emissions 'already in the atmosphere'
• prior warming masked by the cooling effect of aerosols that may decline

 

Infrastructure Inertia

 

Even if humanity commits to a near-elimination of human-caused CO2 emissions, energy and transportation infrastructure have long lifespans that represent substantial CO2 emissions commitments for the next 50 years (Davis et al., 2010).   This infrastructural inertia "may be the primary contributor to total future warming commitment" (p. 330).

 

Committed Emissions

 

In a hypothetical example where future CO2 emissions are limited to CO2-emitting devices that exist now, researchers estimate that those emissions (from 2010 to 2060) would allow a stabilization of atmospheric CO2 below 430 ppm and an average warming to reach about 1.3°C above pre-industrial levels.  For comparison, scenarios that allow CO2-emitting infrastructure to expand resulted in warming of 2.4°C to 4.6°C by 2100 and atmospheric CO2 of more than 600 ppm.

 

Warming Locked In

 

Globally, warming of close to 1.5°C above pre-industrial times (up from about 0.8°C in 2014), is already locked into the earth system by past and predicted greenhouse gases (World Bank, 2014).

 

Need for Alternatives

 

The researchers note that CO2-emitting infrastructure that existed in 2010 was not enough to push atmospheric CO2 and global warming beyond guardrail targets of 450 ppm CO2 and 2°C.  They caution that it is the CO2-emitting infrastucture not yet built that exposes the world to the most threatening climate impacts.  Avoidance of this scenario requires extraordinary efforts to develop alternatives (Davis et al., 2010).

 

Climate Change Commitment

 

A number of climate studies have used models to run simulations that identify and quantify delayed climate changes and impacts in hypothetical stabilization scenarios.  These studies enable scientists to learn how the earth can be expected to respond to a cessation of GHG emissions that warm the climate system, and of aerosols that mask some of the GHG warming.  They show that the greatest inertia (delayed response) is found the oceans, and that some inertia is found global temperature levels. 

For example, Meehl and his co-investigators (2006) created a hypothetical scenario where greenhouse gas concentrations in 2000 remained the same for the next 100 years. The multiple simulations they ran showed that "we are already committed to 0.4°C more global warming by the year 2100 compared to 0.6°C observed warming realized by the end of the twentieth century" (p. 2603).  Further, temperature shows signs of levelling off 100 years after atmospheric GHG levels stabilize.

Sea level shows greater inertia than global temperature.  Sea level increases rose more than double observed increases in the prior 100 years (1901 to 2000).  By 2100, the 'Meehl simulations' show a continuing upward trend. 

If the world suddenly stopped burning fossil fuels the first of January next year, atmospheric CO2 would quickly stabilize.  But temperature and sea level would continue to increase increase long after.  Scientists refer to this delayed stabilization of temperature and other climate impacts as "climate commitment."

 

Irreversibility

 

A large fraction of climate change is largely irreversible on human time scales, unless net anthropogenic CO2 emissions
were strongly negative over a sustained period.  See IPCC AR5, Ch 12, p. 1033.

 

Aerosols

 

Matthews and Zickfeld (2012) estimated that full elimination of aerosols results in warming of between 0.25°C and 0.5°C in the decade after their elimination.

 

Takeaway

 

Delayed responses already in the system heighten the urgency for taking immediate action to build and implement alternatives for CO2 and GHG-emittig infrastructure that are in use now.

 

Links

 

IPCC '07  AR4 WGI | 10.7.1 | Climate change commitment to year 2300

IPCC '01  Human influences to keep changing atmosphere during 21st Century

Nature '05  Oceans extend effects of climate change

World Bank '14  Turn Down the Heat [2014 report]

 

References

Armour, K. C., & Roe, G. H. (2011). Climate commitment in an uncertain world. Geophysical research letters, 38(1). doi:10.1029/2010GL045850 [GRL + .pdf]

Davis, S. J., Caldeira, K., & Matthews, H. D. (2010). Future CO2 emissions and climate change from existing energy infrastructure. Science, 329(5997), 1330-1333. doi:10.1126/science.1188566

Friedlingstein, P., & Solomon, S. (2005). Contributions of past and present human generations to committed warming caused by carbon dioxide. Proceedings of the National Academy of Sciences of the United States of America, 102(31), 10832-10836.

Gillett, N. P., Arora, V. K., Zickfeld, K., Marshall, S. J., & Merryfield, W. J. (2011). Ongoing climate change following a complete cessation of carbon dioxide emissions. Nature Geoscience, 4(2), 83-87. doi:10.1038/ngeo1047

Meehl, G. A., Washington, W. M., Santer, B. D., Collins, W. D., Arblaster, J. M., Aixue, H., . . . Strand, W. G. (2006). Climate change projections for the twenty-first century and climate change commitment in the CCSM3. Journal of Climate, 19(11), 2597-2616.

Matthews, H. D., & Zickfeld, K. (2012). Climate response to zeroed emissions of greenhouse gases and aerosols. Nature Climate Change, 2(5), 338-341. doi:10.1038/nclimate1424

Wigley, T. M. L. (2005). The climate change commitment. Science, 307(5716), 1766-1769.

 

C Budget

Carbon Budget

 

Cumulative carbon budget

IPCC on budget

Link to zickfeld on time for budget.

Link to GCP about budget used.

Policy choice = how much left to use

 

Huffington Post '15 Mann | How close are we to dangerous warming?