guest post by Steve Easterbrook
(2) Humans caused the majority of it
The summary for policymakers says:
It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.
(Box 13.1 fig 1) The Earth’s energy budget from 1970 to 2011. Cumulative energy flux (in zettajoules!) into the Earth system from well-mixed and short-lived greenhouse gases, solar forcing, changes in tropospheric aerosol forcing, volcanic forcing and surface albedo, (relative to 1860–1879) are shown by the coloured lines and these are added to give the cumulative energy inflow (black; including black carbon on snow and combined contrails and contrail induced cirrus, not shown separately).
This chart summarizes the impact of different drivers of warming and/or cooling, by showing the total cumulative energy added to the earth system since 1970 from each driver. Note that the chart is in zettajoules (1021J). For comparison, one zettajoule is about the energy that would be released from 200 million bombs of the size of the one dropped on Hiroshima. The world’s total annual global energy consumption is about 0.5 zettajoule.
Long lived greenhouse gases, such as CO2, contribute the majority of the warming (the purple line). Aerosols, such as particles of industrial pollution, block out sunlight and cause some cooling (the dark blue line), but nowhere near enough to offset the warming from greenhouse gases. Note that aerosols have the largest uncertainty bar; much of the remaining uncertainty about the likely magnitude of future climate warming is due to uncertainty about how much of the warming might be offset by aerosols. The uncertainty on the aerosols curve is, in turn, responsible for most of the uncertainty on the black line, which shows the total effect if you add up all the individual contributions.
The graph also puts into perspective some of other things that people like to blame for climate change, including changes in energy received from the sun (‘solar’), and the impact of volcanoes. Changes in the sun (shown in orange) are tiny compared to greenhouse gases, but do show a very slight warming effect. Volcanoes have a larger (cooling) effect, but it is short-lived. There were two major volcanic eruptions in this period, El Chichón in 1982 and and Pinatubo in 1992. Each can be clearly seen in the graph as an immediate cooling effect, which then tapers off after a a couple of years.
You can download all of Climate Change 2013: The Physical Science Basis here. Click below to read any part of this series:
- The warming is unequivocal.
- Humans caused the majority of it.
- The warming is largely irreversible.
- Most of the heat is going into the oceans.
- Current rates of ocean acidification are unprecedented.
- We have to choose which future we want very soon.
- To stay below 2°C of warming, the world must become carbon negative.
- To stay below 2°C of warming, most fossil fuels must stay buried in the ground.
Climate Change 2013: The Physical Science Basis is also available chapter by chapter here:
Chapters
- Introduction
- Observations: Atmosphere and Surface
- Observations: Ocean
- Observations: Cryosphere
- Information from Paleoclimate Archives
- Carbon and Other Biogeochemical Cycles
- Clouds and Aerosols
- Anthropogenic and Natural Radiative Forcing
- Evaluation of Climate Models
- Detection and Attribution of Climate Change: from Global to Regional
- Near-term Climate Change: Projections and Predictability
- Long-term Climate Change: Projections, Commitments and Irreversibility
- Sea Level Change
- Climate Phenomena and their Relevance for Future Regional Climate Change
Azimuth 
Dear Steve, if I were you, before disseminating nonsense to a wide audience, I’d perform at least some sanity check.
According to Box 13.1 fig 1(a) current rate of energy accumulation in the climate system (Total energy) is 31 ZJ/year, which can be anything between 18 ZJ/year and 41 ZJ/year due to uncertainties, mostly in Tropospheric aerosols.
On the other hand we have data for heat contet of the upper 2000 m of oceans since the beginning of 2005 from NOAA NODC OCL. During the past 8 years rate of heat accumulation in this particular heat reservoir was less than 8 ZJ/year. This is based on actual measurements collected by the ARGO network.
Trouble is there’s no heat reservoir in the climate system other than the upper ocean which could store the difference, neither have tropospheric temperatures increased during the last one and a half decade (a.k.a. “pause”), making temperature induced increase in radiative losses to space impossible.
Therefore the IPCC has 23 ZJ/year (something between 10-33 ZJ/year) on its hands, which has nowhere to go. That’s huge.
Berényi Péter wrote:
I’m sorry, but this is the sort of rudeness I don’t allow here. The issue you raise is important, well-known and worth discussing; the problem is that you’re treating this as the start of a fight rather than a friendly conversation. Further comments of this nature (or comments on my moderation policies) will be deleted.
Let’s just enjoy discussing the science! You were once the victim of rudeness here, for which I apologize, so you should know how unpleasant it is.
Well, there’s the deep ocean!
Before continuing, I hope everyone reads these:
• Magdalena A. Balmaseda, Kevin E. Trenberth and Erland Källén, Distinctive climate signals in reanalysis of global ocean heat content, Geophys. Res. Lett. 40 (2013) 1-6.
• Norman G. Loeb, John M. Lyman, Gregory C. Johnson, Richard P. Allan, David R. Doelling, Takmeng Wong, Brian J. Soden and Graeme L. Stephens, Observed changes in top-of-the-atmosphere radiation and upper-ocean heating consistent within uncertainty, Nature Geoscience 5 (2012), 110–113.
(I haven’t found a free version of the second one, alas.)
There’s a lot of useful background information here:
• Trenberth can’t account for the lack of warming, Skeptical Science.
Why did you choose this graph of just inputs? What is (relative to 1860–1879)? All the components start at zero in 1970, does the “relative” information just apply to the last aerosol component? If it is all components, and what is being accumulated is the amount of those forcings to the extent they are different from that 19th century range, then the slopes might be quite steep, even if there is no change in forcing since 1970. Changes since 1970 would only be represented in changes in the slope. 40 years is not really long enough to be climatic, since multidecadal ocean modes like the PDO have are about 60 years.
I chose to use this graph because it’s an excellent way of visualizing the relative magnitudes of different forcings in the recent past. It doesn’t show “just inputs”, it shows accumulation. Confusion between inputs and accumulation is common in discussion about climate change, which is unfortunate, because it’s accumulation of energy that really matters in terms of impacts on humans. You imply the graph might be misleading, because you can’t easily see whether there are changes in forcings since 1970. If you want to see that, sure, use a different chart. But the key point of this chart is that even if the forcings were constant since 1970 (and they most definitely weren’t!!), it doesn’t matter much, because heat still accumulates in the earth system, and will continue to do so until the planet reaches a new thermal equilibrium. The actual level of any forcing at any moment in time doesn’t really affect us. The accumulation of heat energy over time in response to a changed forcing does.
BTW I also like how this graph puts into context many things that contrarians like to suggest are more important than greenhouse gases. For example, the graph clearly shows the impact of changes in solar forcing is tiny compared to the GHG forcings. It also clearly shows that volcanoes do matter (and, contrary to popular opinion, they are taken into account in climate modelling!), but that each major volcano represents a small step change in the accumulation curve, which is quickly swamped by the long term effect of GHGs.
Where is the chart from? It is not the same chart in WG1AR5_SOD_Ch13_All_Final.pdf, and I don’t see any reference to “relative to 1860–1879”. Furthermore the (a) chart in the document, is not the accumulation in the system that gets stored, it is just the cumulative input. It is (b) that gives the destination of that energy, most gets radiated, and about 300 10^21J gets stored in the oceans.
Also the reason it actually would be interesting if 1860-1879 is the base period for the forcings, is because that would be an inappropriate base for the solar contribution, it one was trying to attribute heat storage into the ocean. By that time solar forcing was already above that of the Little Ice Age and the Maunder Minumum, glaciers were retreating, etc. So there were several centuries of heat storage in the deep ocean to come before equilibrium with this higher level of solar forcing. Of course solar forcing continued to rise until it plateaued at a high level in the middle of the century.
From the text of the charts in chapter 13, the radiative flux being accumulated is not just from the forcings themselves, but are enhanced with feedbacks under an assumption of 3.0C climate sensitivity, and apparently that the feedbacks to the forcings are all the same despite, the knowledge that forcings couple to the climate differently. To quote Knutti and Hegerl (2008):
“The concept of radiative forcing is of rather limited use for forcings with strongly varying vertical or spatial distributions.”
and this:
“There is a difference in the sensitivity to radiative forcing for different forcing mechanisms, which has been phrased as their ‘efficacy’”
The chart appears to actually be from the technical summary TFE.4
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