Attribution of Recent Climate Change to Human Causes

There are serious climate scientists who  believe that 110% of recent climate change is due to human emissions of CO2. They think that natural variability is pushing down temperatures, canceling 10%  of the effect of our greenhouse gases. There is apparently no room in their world for deforestation, black soot, etc. Greenhouse gases uber alles!

Humans do a number of things that affect the climate.  Emitting greenhouse gases is the one that gets all the attention. But deforestation, black carbon, aerosols, changes in land use and land cover, reservoirs behind dams, all change the climate. Production of cement is estimated to emit 5% of all CO2. That’s as much as is estimated for air travel.

I haven’t seen a table anywhere that shows the estimated contributions as a percentage of the whole. What I have seen are charts of those that contribute to radiative forcing, such as this one:


But I’d like to see a list of all contributions to global warming, such as black carbon. Back in 2001, Stanford scientist Mark Jacobsen wrote, “”Soot -­ or black carbon ­ may be responsible for 15 to 30 percent of global warming, yet it’s not even considered in any of the discussions about controlling climate change.”

Then for 13 years we didn’t hear about it anymore. It resurfaced last year, but without percentage estimates.

When I first started covering climate change, deforestation was estimated to contribute 20% of our greenhouse gases. Now it’s down to 17%, due in part to lower deforestation but sadly also in part due to an increase in total emissions.

So, another bleg–does anyone have such a chart at hand?

It’s important. If we don’t have a simple attribution figure that is widely agreed on, we will not get the support we need.

This is the second part of the RAMA Initiative. Part 1 was Recognition. We spent a week with Viscount Monckton establishing that even a staunch skeptic is capable of recognizing climate change and that humans are capable of causing it. Attribution much exist and be accepted before we even talk about Mitigation and Adaptation, the other two components of the initiative.

So thanks in advance for the help.


12 responses to “Attribution of Recent Climate Change to Human Causes

  1. Let’s see, this is the forcing versus a baseline. Should we assume the baseline is X CO2, Y CH4, etc?

    Let’s focus on methane (mostly because I’ve been reading about it). Methane sources seem to be (in no particular order) 1. Rice paddies, oil and gas industry, garbage dumps, coal mines, cattle….

    So are you trying to see what’s the attribution to each of these sources at this time? I guess you will need a historical record of these contributors. Right?

    How do you handle the water vapor feedback? Say we have been putting increasing amounts of methane in the air as we increased rice cultivation. This in turn has raised temperature and created a positive water vapor feedback. Do you include the feedback attributed to methane in this chart?

    • Methane is tough. It occurs naturally but sporadically. It is also created by human activity. What percent of animal methane emissions is natural and what percentage is cultivated by man?

  2. Am I missing something? I thought water vapor was supposed to be the big amplifier. Where is it?

  3. The black carbon effect is accounted for in the albedo term, which has positive and negative components.

    The water vapor feedback is a feedback, not a forcing. It responds to the net of the other terms.

  4. Tom, I have trouble reading the graph but it seems to be heavily influenced by the Phil Jones papers of the late 80’s and early 90’s.
    Saying that albedo changes are a net cooling is cooking the books. The biggest changes are where they will have the greatest feedback— soot on arctic snow.
    I don’t see heat capacity.
    The biggest term in man made climate change is probably increased heterogeneity of albedo and heat capacity. No ones talking about it but Peilke sr and a few of his buddies.

    Some time ago, I sent you some files on Louis Thompson’s research. Maybe this is the time to reintroduce them to the debate. Louis was Dean at ISU when he retired.

  5. Pingback: Forward Blogging Schedule and This’n’That | The Lukewarmer's Way

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