This is an important topic, how do we know what we know, and how do we know it’s right?The first thing you need when you start your journey towards any competency in any discipline, is to forget everything you were taught and believed that was wrong.
This is harder than it sounds, but I hope this will help while serving as a warning.All scientific knowledge is tentative, this is what we know today, this might all be wrong tomorrow. But until tomorrow, treat everything as validated evidence.There are no proofs in science, you have hypothesis and once they’ve been validated, theories.
There is no “right or wrong” just validation and falsification.“Science” is the application of the “Scientific Method” this means knowledge gained by observation, hypothesis, experimentation, and evaluation. It isn’t gained through consensus of opinions or agreeing with past superstitions. “Consensus” only means the current theory has no competing theories at this time- if might tomorrow, it might not.
Theories describe how the universe works, laws are mathematical constructs: Laws define the way the universe works without explaining how- they combine variables and constants in specific equations.Our observations of the universe help us produce models used to project future events, or understand what happened in the past. This doesn’t mean it’s a perfect model, but good enough to allow a better understanding.
And this is where I am going to lose many of you, because these concepts can be hard to understand, but this is exactly what I meant earlier- to really comprehend science you have to unlearn the ideas you were taught that were wrong.Everything is a model.
Everything we measure, is a model of behaviors that help us understand how that information can be converted from an intangible concept into reality, even if it’s only a model of reality. Temperature is the average random kinetic energy in a sample, and we have never measured temperature directly.Never.We have measured the effect that temperature has on an enclosed volume of liquid, either mercury or alcohol. We measure how much that liquid expands, and by analogy we measure the change in temperature. Change in volume is our proxy model to try to explain and measure change in temperature.
Or we measure the difference in deflection between two different metals stamped together (this is how mechanical thermostats work). When this is shaped in a spiral coil, we can easily add a needle to the center of that coil and see that needle move from one side to another. That’s your typical oven thermometer, or older style refrigerator thermometer- maybe even something you stuck into a turkey.
Two wires made of two different metals generate a voltage at the point immediately after the two separate – measuring that voltage gets you a proxy measurement of temperature. It can also generate a tiny amount of power, this is a thermovoltaic cell (more about this in another episode.)
A very precise thickness of wire, preferably something very stable like platinum, has a changing resistance with temperature. Measure that resistance indirectly (pass a fixed current through that, you get a varying voltage) and you get a proxy measurement of temperature.A very common semiconductor (the most primitive of all) called a diode has an almost similar effect to the bimetal
The voltage drop across that diode varies with temperature. This might be the most common way we measure temperature today.We’re not done yet! The frequency and intensity of infrared light a material gives off (earlier episode) gives us a proxy measurement of the temperature of that material. This is much more complicated and gives you not just a bulk temperature of a material but a possible infrared (or microwave) image of that, it’s the heat map made famous in the Predator movies. Also useful in finding out where your windows are leaking a draft.
All temperature measurements are proxies. But that’s not all- as mentioned earlier we use the differences in oxygen isotope concentrations to help us project what temperatures were in the past. The same concept, isotopic ratios act as a proxy that helps us figure out a sample’s age.So now it’s time to have some fun! Step on a scale, the springs compress, that spins a dial which indicates your weight (mass times local gravity).
Another one pushes a tiny magnet down which changes the magnetic field in a Hall Effect sensor, creating a voltage proxy that we use to “measure” weight. Take a sample of alcohol and put it in a device that shines a light through it- the change in the light’s direction as it goes through the solution shows us the index of refraction of that liquid, that’s an indirect way of measuring it’s alcohol percentage.
Or in a slightly different instrument, it’s sugar content. Measuring the resistance between two fixed electrodes tells us the ionic concentrations of a fluid. Fire an atom or molecule with a charge through a magnetic field, and see how far it deflects away from a straight-line path- that tells us how heavy the sample is and can tell us which specific isotope we’re measuring. Heat up that material and see the colors of light it gives off- that tells us its exact chemical makeup Firing a light through a gas and seeing what colors are no longer there does the same thing- molecules or atoms that generate frequencies of light, absorb the same frequencies. Depending on where our sample is, we can use different techniques to come to the same conclusions.
When we know how materials work, how they interact with light or temperature or pressure or any of hundreds of esoteric properties, we can use those principles, those models to measure the physical world. All instrumental measurements are models of the behavior of matter and materials, and by using those models we interrogate reality.
The more we learn about materials and the way they change and interact with time or in the presence of other objects or fields, the more proxy solutions and often we have more than one way to measure the same thing- this is called “cross calibration”.
We have 5 (that I know of…) different isotopic ratios that are accurate enough and easy enough to measure for objects roughly the age of our planet- using all five of these allows a sharp reduction in the uncertainty of measuring the age of earth.
When we measure samples, either past or present, we can be relatively well assured that the interrogation methods we use are accurate enough for us to get the information needed to improve or validate our models of reality. Now for the scary part- our abilities are very recent, and are improving with every day. 

Here Comes the Sun

You knew we had to get to this eventually- you’ve heard me say this before, when it comes to climate change, “it ain’t the sun.” Welcome to lesson 6, “Here comes the sun.”

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~4.6 billion years ago the stellar nebula we came from coalesced into our sun earth, other planets & the rest of the stellar neighborhood. Stars are at constant equilibrium between gravity pulling them together & heat pushing them apart, once gravity becomes strong enough.

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Hydrogen within the core gets hot enough to fuse into different forms of hydrogen & helium. As atomic nuclei get larger they lose microscopic amounts of mass, that reduction generates heat as "spare

neutrons fly out of the new nuclei.

Atomic particles have 3 charges:

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Positive, neutral, & negative.

Like charges repel each other, opposites attract. Jamming together more positive particles (protons) sends neutral particles (neutrons) flying out of the atomic nucleus.

Three forms of Hydrogen: The basic H1 w/a single proton in the nucleus.

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The other hydrogens have 1 & 2 neutrons in the nucleus- keeping it simple- protons can change into neutrons and positrons. Add 2 H³ atoms together yields a new He4 atom along with 2 extra neutrons flying apart at high speeds- that’s random kinetic energy:

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Temperature again, bangs solar gasses into each other, eventually reaching the surface converting that energy into visible light. As astonishing as it sounds, energy density of the sun is orders of magnitude less than our bodies!

It’s also1.3 million times bigger than earth.

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A minor problem, the Hydrogen to Helium cycle doesn’t generate as much energy as the later Carbon-Nitrogen-Oxygen cycles, they start off being relatively cold, & the get hotter over time.

Over a very, very long time, currently ~ 1% hotter/114 million years.

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In ~6-10 billion years the sun will stop most of its fusion & it’ll rapidly cool, it’s outer layers immediately expanding, possibly with sufficient force to envelop the earth before gravity stabilizes it again. Before that it’ll get too hot for liquid water at the surface.

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But right now, our sun is an extraordinary example, it’s one of the most stable stars we’ve ever seen, roughly 9000 years of proxy data shows this sun has on a decade-by-decade basis, varies by less than 1/10th of a percent.

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We have over 75 years of observatory and satellite data showing an even more stable sun, varying by between +0.04 and -0.08% for a 121 day rolling average. When we compare solar output to 2 meter surface temperatures, we find it has little effect on climate.

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When we detrend the nearly linear temperature changes and compare them to ENSO3.4 and insolation, we see El Ninos have a slightly higher influence: still less than 1/10th °C.

So it’s not the sun, and both El Nino and the sun balance out over time, doesn’t this suggest other sources for measured climate change? It’s still greenhouse gas emissions.

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The laws of mean planetary surface temperature is fascinating, temperature of a planet’s surface w/out greenhouse effect is based on the incoming energy to the -4th power. If solar energy increases by 4.1%, the planet’s temperature increases by 1%.

What's a 0.1% change?

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Basic rule of thumb unless there’s feedback or albedo change caused by ice loss or growth a 0.1% increase /decrease in solar energy received by the earth’s surface changes global mean surface temperature up or down by ~0.07°C

Lately about 2.5 years of global warming.

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In about a billion years, the earth will again have a supercontinent near the equator with large seas in the Arctic and Antarctic, they will not have ice caps, they will not reflect much light back to space. The ~8% hotter sun will in years with highest eccentricity 

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Get extremely hot- hot enough to slowly boil water away from the atmosphere. Unless cloud cover diffuses the sun much more so than now, we will slowly evolve away from a blue water covered planet to a much hotter, dryer world. Eventually the sun will control climate in ways we don’t want to imagine.

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15A This is a return to my former style, because this topic was much more technical I added charts and technical references, including equations (Stefan-Boltzmann’s law). This was complex, I hope there are questions and I hope I can answer them! Thanks for your time, see you soon