Let’s Review: How We Know Climate Change is Human Caused

October 16, 2018

Do we have to do this again? We do.

Due to high demand from journalists and others as to the “Sure, the climate is changing but how much is due to humans?” – talking point rolled out in back to back interviews from Donald Trump and Senator Marco Rubio – experts Stefan Rahmstorf and Andrew Dessler have offered some tweeted primers.

Stefan Rahmstorf:

How do we know global warming is human-caused? Because we know where the extra energy that heats our planet is coming from. Through changes in the energy budget of Earth – that’s how much radiation comes in, how much goes out. The change in this is called “radiative forcing”.

Possible causes of radiative forcing: changes in solar activity, in volcanic activity or greenhouse gases. The latest US Climate Assessment shows how much each of these contributed. See The human contribution is about 100%. That is: all of it.

forcings

How do we know the rising CO2 in the atmosphere is 100% human-caused? Because we’ve added about twice as much fossil CO2 to the atmosphere as is needed to explain the observed increase! The rest that’s not in the atmosphere was taken up by forests and the ocean.

Andrew Dessler:

We do know that the observed warming of the climate system is extremely likely to be caused by human emissions of carbon dioxide and other greenhouse gases.

The logic is as follows: we know theoretically that adding a greenhouse gas the atmosphere should warm the climate.

We also know that we are adding greenhouse gases to the climate, so one should expect a warming trend.
And the observed warming is about the magnitude that we would expect from warming induced by greenhouse gases — as evidenced by the fact that, if you put that much greenhouse gases into a climate model, you get about the observed warming.

To be really confident, however, you also have to eliminate the other suspects. We have a pretty good idea of what other mechanisms could be causing warming (changes in the Sun, internal variability, etc.).

We have investigated them all and find that none of them can explain the timing and magnitude of the warming nearly as well as greenhouse gases.

The scientific community therefore concluded that humans are extremely likely to be responsible for most of the warming since the mid-20th century.

This theory is extremely successful and predicted a lot of the things we now observe — i.e., cooling in the stratosphere, heating in the oceans, the overall pattern of surface warming.

If you think you have a better theory of climate, then this is what you need to do.

step 1: you have to show the governing equations; i.e., temperature as a function of the key variables; T = XXX or dT/dt = XXX

step 2: then you must show this reproduces key observations. Mainstream theory explains just about everything, so ur theory should too.

step 3: if you want to superced mainstream climate theory, you must show your theory explains something that mainstream theory doesn’t.

– one of the reasons people believed general relativity was that it explained the orbit of Mercury, which Newtonian mechanics doesn’t.

One more, h/t @JohnMashey: given evidence that CO2 traps energy, you also have to explain why that’s NOT causing climate to shift.

Yet one more h/t @ericsteig: if your theory makes a non-obvious prediction, that will be very convincing.

e.g., general relativity makes prediction that position of stars is different during eclipse. That was confirmed, convincing scientists.

 

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12 Responses to “Let’s Review: How We Know Climate Change is Human Caused”

  1. grindupbaker Says:

    I rented out a high-rise apartment I owned 20 years ago for my work relocation. A lady phoned with “Is it spacious ?” I’d made a Floor Plan (I measure everything I can in life) and gave her the width & depth of its footprint, 2 largest rooms, enclosed balcony, plus the general layout (open kitchen). She said “Yes, but is it spacious ?”

  2. rabiddoomsayer Says:

    “Humans are responsible for 100%” I would argue it is 100% plus some, actually plus a lot. We have interupted a natural cooling cycle and have been for much longer than just the last 150 years. Do you have a better explanation than William Ruddiman https://www.youtube.com/watch?v=96loo1w3SLY

    • neilrieck Says:

      100 years ago, one human could cut down then burn a tree which represents the carbon and solar energy collected by that tree over ~ 30 years. Today, one modern human can burn carbon and solar energy collected by the biosphere over tens of thousands to tens of millions of years. Now not everyone of the 7.1 billion humans on the planet are modern, but they aspire to be. And capitalism works to make it possible.

      • J4Zonian Says:

        Capitalism is a tool used by our psychological condition to express its rage, shame, fear, and ultimately the emptiness caused by inappropriate infancies and childhoods that causes all those emotions. We need to reorganize our relationships to each other and the rest of nature to give up that tool, or whatever we pick to replace it will be just as much an expression of all that and will be just as bad.

        • dumboldguy Says:

          “….the emptiness caused by inappropriate infancies and childhoods…”????

          JFC! Will you ever get beyond the ignorant psychobabble and deal with the basic SCIENCE that explains how we have arrived at “…will be just s bad”? Read up on evolution, adaptation, and natural selection.

          The human species has evolved far enough to employ all this “technology” (including capitalism) that is destroying the biosphere, but has NOT evolved far enough to be able to foresee the future damage or undo it in time to avoid climate catastrophe. Darwin would understand, why don’t you?

        • J4Zonian Says:

          People looking for something to blame the climate crisis on, but unwilling to face the obvious truth are constantly pointing to other things–volcanoes, the sun, natural cycles, outright denial, capitalism, people of color, whatever. They often lash out with anger to avoid facing the reality of their fear.

          Similarly, it’s often those most desperately and obviously in need of psychotherapy who seem most contemptuous of it. In defensiveness over what they feel might expose them and force them to be aware of their fear–whether it’s climate catastrophe or psychotherapy–they resort to any number of tactics, including retreat into a rigid pseudo-logic or exaggerated concreteness. It’s ultimately untenable because it denies the complexity of reality, but their defensiveness, aggression and other tactics in combination, often drag out conflict for a long time. And often their inability to step out of their concreteness, or simply their lack of intelligence, makes it impossible for them to understand the complexity of the world. They can become frustrated and venal and react to every tiny stress by attacking anyone they can convince themselves is the cause of their suffering. It’s unfortunate—tragic, in fact—for them and the rest of us who have to put up with their acting out, especially when the solution is so obvious.

          • dumboldguy Says:

            “Similarly, it’s often those most desperately and obviously in need of psychotherapy who seem most contemptuous of it”. Contemptuous? Really? Says who, Jeffy? Can you cite someone with expertise in things psycho? You are just setting up another false premise on which to build another ignorant argument—-how clever of you!

            All that follows is just more “psychobabble”—-a feeble and transparent attempt at an attack. Yes, the solution is SO obvious—you need to get educated so that you can talk intelligently about “the complexity of the world”, grow the F*** up, and start talking about the science of climate change here—-we are getting tired of your “acting out”.

            If you try hard enough, you can overcome “….the emptiness caused by (your) inappropriate infancy and childhood” and become a contributing member of Crock. (Note that I have NOT suggested that you kill yourself, although that may be the only cure for your terminal case of anal orificism).

      • dumboldguy Says:

        Some numbers to add into any equations that may be forming in Crocker’s brains:

        In 1917—-1.9 billion humans total on Earth
        In 1940—-2.3 billion (year I was born)
        In 2018—-7.7 billion
        (It has more than tripled in my lifetime, quadrupled in last 100 years)

        If anyone wants to see an extreme hockey stick, look up a graph of human population from 10,000 BC to the present.

  3. neilrieck Says:

    Not sure how many people here still listen to Science Friday (the TEA-party was responsible for getting a Republican congress to defund NPR by 90%) but a scientist phoned in on Oct-12 and basically said “high temperatures are killing the pollen of various US crops”
    https://www.sciencefriday.com/

  4. rhymeswithgoalie Says:

    People whose eyes glaze over when you explain the physics of GHGs in the atmosphere might instead be able to accept the fact that Venus is hotter than Mercury, despite its being farther from the sun.

    • dumboldguy Says:

      Have you checked with your friendly neighborhood Flat-Earther about that? Mine says Venus and Mercury are just lights in the sky.


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