Climate Change Part 7: Green House Gases 2

Note: This program first aired May 5, 2014.

When last we talked about climate change, we left off with the idea that more energy comes into Earth’s climate system than leaves. Heat is essentially building up in the atmosphere, less heat is escaping back into space than is coming in in the form of sunlight. The reason for this is a change in the amount of greenhouse gasses in the atmosphere.

When we look up into the sky we see what we think of as nothing. But far from it, the sky is full of matter, billions upon billions upon billions of atoms are floating around up there. And these atoms, just like many others, absorb infrared radiation, which is simultaneously being released by every atom everywhere, every atom that isn’t absolute zero. The Earth is radiating infrared radiation, as a result of having been hit with light from the sun. That light (a narrow relatively high energy band of the electromagnetic spectrum) gets converted into a longer wavelength, lower energy form, infrared radiation, and infrared radiation is the form in which the Earth loses the energy that it originally gained as light from the sun. If there were no atmosphere, if when we looked into the sky what we really saw was nothing, the Earth would be much colder than it is now because all the infrared radiation it is emitting would easily escape into space. Much like a human being, running around in the winter naked. Heat readily leaves the warm human body, and with nothing there to stop it, the human rapidly cools. That naked human can slow the escape of heat from her or his body by putting on clothing, creating a warmer microclimate around the body, thus reducing their convective, evaporative, and radiative losses.

The Earth loses energy by all of those means as well. Sunlight comes in and warms the air. Warm air rises, transporting that heat higher into the atmosphere, moving it closer to space. Likewise, water absorbs that light energy and warms up, evaporating more readily. When water changes phase from liquid to gas, it takes a great deal of energy with it. When that water vapor makes its way up into the atmosphere and condenses into water droplets to form clouds, it releases that heat, again, high in the atmosphere, where it is more easily lost to space. The current imbalance in Earth’s energy budget is due to the radiative losses (or lack there of), the fraction of the sunlight that makes it to the surface of the Earth that doesn’t just go into heating air or evaporating water. That light is simply absorbed by matter here and reradiated back out as infrared radiation.

That infrared radiation doesn’t all make it back out into space right away, because of green house gasses. The green house gasses are water vapor, carbon dioxide, ozone, methane, nitrous oxides, and chloroflourocarbons. All of them except the CFC’s are naturally occurring gasses, and without them, the Earth would not be livable, so green house gasses aren’t a bad thing. Each of them absorbs specific wavelengths of infrared radiation, with water vapor absorbing the widest range of wavelengths (that is why it is the most important green house gas!). There is a gap in the absorption spectrum of water vapor though, from about 8 to 14 microns, a micron is a micro meter, a millionth of a meter. That gap is essentially a hole that infrared radiation can escape through, because any radiation with wavelengths between 8 to 14 microns won’t be absorbed! Most of the green house gasses overlap their absorption spectrums with water vapor, meaning they absorb the same kinds of wavelengths that water vapor does. But carbon dioxide is different. It absorbs wavelengths of around 12 and 13 microns, meaning, it partially plugs that 8 to 14 micron hole in the water vapor absorption spectrum. Because the hole that infrared radiation can escape through is getting smaller due to being partially plugged by carbon dioxide, less heat can escape the atmosphere. When less heat escapes, more heat stays around to warm things up here on Earth.

Remember, there has always been a lag time between heat getting radiated from Earth and heat getting lost to the atmosphere. That is what makes Earth’s average temperature greater than zero, and that is a good thing, at least for us. When climate is stable, that “lag time” is consistent, which means the back log of heat leaving through the atmosphere is consistent. What is happening now is, due to the extra carbon dioxide  in the atmosphere, the lag time is increasing, and the back log of heat is getting bigger, so Earth’s average temperature is warming. And it is just due to the slight narrowing of this atmospheric window. That is why we pay so much attention to carbon dioxide as a green house gas, it is the atmospheric factor that is effecting the biggest change in the heat balance of the Earth. Next time we will look at an example from Earth’s history, of a period that experienced the same kind of rapid warming we are beginning to, as it may give us a sense of what we can expect.

References:

Scroll down this page from Texas A&M University to see a graph of the absorption spectra of several green house gasses: http://oceanworld.tamu.edu/resources/oceanography-book/radiationbalance.htm

Climate Change Part 6: Green House Gases

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Note: This program first aired on April 12, 2014.

So far we’ve talked about how the amount of energy reaching the Earth can change, though differences in the amount of energy the Sun emits and variations in what the Earth reflects back into space as light. The last big player in climate change affects not how much energy reaches the Earth, but how much is kept here.

Recall that the energy that drives the climate system comes from the Sun arriving as light. Light is a high energy, short wavelength form of radiation, and the Sun emits light because it is so hot. About 30% of the light that hits Earth is reflected back into space, due to the reflectivity, or albedo, of certain Earth surfaces. That leaves approximately 70% to actually reach Earth and enter the climate system. Of that 70%, about 20% of the visible light is absorbed by gasses in the atmosphere. We’re more familiar with the phenomenon of atmospheric gases absorbing certain wave lengths of solar radiation when we talk about the stratospheric ozone layer. The ozone molecule, O3, is found at low but important concentrations 15 to 30 kilometers above the surface of the Earth. It plays an important role in the history of life on Earth, because it absorbs some of the non visible radiation that comes from the sun, ultraviolet light. UV light is particularly damaging to cells (skin cancer anyone?), and without the filtering effect of stratospheric ozone, it would have been hard for life to evolve, or the life that did evolve, would look pretty different.

It turns out that ozone absorbs visible light as well, as does water vapor in the atmosphere, and even carbon dioxide to a limited extent. Any non reflective particulates (dust, soot) can also absorb light. This is where that first 20% of energy entering the climate system goes—its absorbed by gases and particles in the atmosphere.

The last 50% of the light energy from the sun makes it to the surface of the Earth and is absorbed there by everything down here-rocks and soils, plants, water, and sunbathers. When that as light energy gets absorbed it gets transformed into infrared radiation, otherwise known to us a heat. The gases in the atmosphere, the rocks and soils, plants, water and sunbathers aren’t hot enough to emit the energy as visible light, so it down cycles into heat. That 70% of light energy from the sun that hits the Earth all gets turned into heat, which is the form in which it is reradiated back into space which is eventually where it will all end up.

When the gases in the atmosphere absorb light and radiate out infrared radiation or heat they do so in all directions. Each molecule sends out its little bit of transformed heat energy, and that energy can then hit another nearby molecule, heating it up, before that second molecule radiates out the heat, and so one. Because the gases in the atmosphere are up so high, quite literally closer to space, it is much easier for the heat they are emitting to make it back out into space. When we get high enough above Earth, the atmosphere is no longer the atmosphere, there are so few air molecules there we call it the exosphere. With so few molecules, when a molecule does radiate some heat, the chances of another molecule absorbing it are much lower, and the chances of it simply going into space are much higher. The net result of this is that a high percentage of the light energy that is absorbed by the gases in the atmosphere gets reradiated back into space, without ever helping us out down here on the surface.

Down here closer to Earth all that heat radiation is a great deal further from space. Again, radiation is happening in all directions, but some of that direction is right back to the surface of the Earth. So simply by distance it is harder for heat at the Earth’s surface to get out into space. The physical process of heat radiation transferring from atom to atom, and the randomness of the direction of travel all play into this. The net effect of this is that of the 50% of the light energy of the sun that reaches the surface of the Earth, a lower proportion is radiated back out into space (at least immediately). This time lag in the functional reemmission of infrared radiation from the surface of the Earth is the reason that we have a livable climate here, why the average temperature of the Earth is something higher than absolute zero. And it is due in part to this backscattering of infrared radiation I’ve just described. But it is mostly due to gases in the atmosphere, green house gases. The specific mechanics of how this process works will be our topic next week.

Climate Change Part 5: The Parts of the system 2

Note: This program first aired on April 5, 2014.

We talked last week about one of the ways that the amount of energy affecting the Earth’s energy balance can change, that being if the amount of sunlight reaching the Earth changes. Changes over time in solar output, as well as minute changes in the distance of the Earth from the sun can influence the energy balance, but only on very long time scales, or to very small degrees, or both.

Another way that Earth’s energy balance can be disrupted is through a change in albedo. Albedo is the reflectivity of a surface, the higher the albedo, the more light is reflected. Reflection is an important concept to understand when thinking about Earth’s energy balance. The sun’s energy comes to Earth as light, but is quickly transformed when that light is absorbed by the oceans, land and atmosphere and is reradiated as heat. Albedo refers to the portion of the sun’s light that is NOT absorbed, but instead simply reflected back into space as light. It hits us as light, and bounces back to the universe as light. Its what makes us visible as the “Pale Blue Dot” that Carl Sagan and the Voyager space craft made famous. Because the light isn’t absorbed and transformed, it does not play any role in Earth’s energy budget. Currently Earth’s albedo is around 0.3, meaning 30% of the light that hits Earth is immediately reflected back to space.

How does that number change? The easiest way is to change the amount of snow and ice on the surface of the Earth, as snow and ice are white, and thus have the highest albedo of all Earth surfaces. Desert sand and grasslands can also have relatively high albedo, but nothing approaching the bright white of freshly fallen snow. When less surface is covered with highly reflective material, less sunlight is reflected, which means that more sunlight gets absorbed by the Earth’s climate system.

Here’s the thing with the albedo of snow, though, and it allows us to introduce another important concept in climate change, the concept of feed back loops, and it goes something like this: the more snow you have, the more albedo you have, the more light you reflect, the less energy stays in the climate system, the cooler it gets, the more snow you get. Likewise, the less snow you have, the less albedo you have, the less light you reflect, the more heat stays in the climate system, the warmer it gets, the less snow you have. These are feedback loops, in which the results of an interaction then influence subsequent interactions. When the interactions result in ever increasing values (and in this case the value we are looking at is temperature), for example the less snow we have, the less we reflect and the warmer it gets as a result, further influencing the amount of snow and thus reflectivity that can remain,  we call that a positive feedback. When the interactions result in decreasing values, the more snow, the more reflection, the less energy in the system, the cooler it gets, that’s a negative feedback. It adds a layer of complexity to understanding the climate system. When the solar output varies, climate can change, but when Earth’s climate changes, it doesn’t influence solar output. Solar output is a truly independent variable. Albedo varies, but often in response to a change in climate. Albedo can change climate, but can also be changed by climate. Complexities like this are why predicting climate change is so incredibly difficult and requires the world’s most powerful super computers to accurately model.

There are a couple other albedo issues to look at. Snow and ice are white and reflective, but what about clouds? They’re white. And its true, clouds can have high albedo, and result in a negative forcing or net cooling influence on climate. But…but, clouds are also very good at trapping heat, infrared radiation, which results in a positive forcing or net warming influence. The albedo of clouds depends strongly on how thick they are and how high they are, and the formation of clouds depends on how much water vapor is in the atmosphere and how much the atmosphere is cooled (water vapor condenses out of air and forms clouds when an air mass reaches its dew point). The effect of clouds is highly variable, and thought, at this point to have a small negative, or cooling impact on the climate system.

The effect of volcanic aerosols is the other place we talk about reflectivity relative to climate. When a volcano erupts, especially if it is a big eruption and it erupts straight up, it ejects lots of material up into the stratosphere. Some of this material is sulfuric acid, which then forms particles called aerosols. Because these aerosols  have been injected way up into the stratosphere, they can disperse around the planet in a matter of weeks, and stay there for a year or more.  They are light colored and hence increase the albedo very high in the atmosphere, which decreases the amount of light energy that reaches the lower atmosphere and surface. Net global cooling is often observed in the year or two after a major volcanic eruption, due in part to this temporary increase in upper atmosphere albedo.

We’ve looked at solar output and now albedo, next time we will look at another big driver of climate change, the so called green house gasses in the atmosphere.

References:

An Atlantic article about Carl Sagan and the Pale Blue Dot: http://www.theatlantic.com/technology/archive/2013/11/the-carl-sagan-of-our-time-reprises-the-pale-blue-dot-photo-of-earth/281414/

All about albedo: http://www.climatedata.info/Forcing/Forcing/albedo.html

Cloud Albedo from the Earth Observatory: http://earthobservatory.nasa.gov/Features/Clouds/clouds.php

Volcanoes and climate effects: http://earthobservatory.nasa.gov/Features/Volcano/

Climate Change Part 4: The Parts of the System

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Note: This program first aired on March 29, 2014.

Last time, we talked about the energy balance, or budget sheet for Earth. Earth’s climate at any given time results from the equilibrium of energy coming in and energy going out. When more energy comes in than leaves, the climate warms, when less energy comes in than leaves, the climate cools. As we are at the beginning of a projected warming period, we need to  look at the pieces of the climate system to see what might be causing the changes we are observing.

This begs the question then, what are the things that can change the energy balance of the Earth’s climate system? The first one doesn’t have anything to do with us, it originates out in space, that being of course, the sun. Anything that can change the total amount of energy from the sun that makes it to Earth can have the potential to change the climate system, if everything else stays the same. Returning to our household budget analogy, changes to the amount of solar radiation are like changes to your pay check. If you get a raise, but nothing else about your budget changes, you end up saving more. If you take a pay cut but maintain the same budget, your savings decrease.

As a star, the sun has a natural evolution that changes the amount of energy it emits. Over the past several billion years, the sun has gotten hotter. It will get hotter, and then cooler as it continues to evolve over then next several billion years. This isn’t a factor in current climate change, because this solar evolution takes place over a huge time scale, billions of years. There is a shorter, 11 year cycle of solar activity, related to sunspots that some scientists have tried to correlate to changes in solar radiation, with varying degrees of success. Other ways that solar radiation can vary are through the Milankovich cycles, periodic changes to the shape of the Earth’s orbit, called eccentricity, the timing of perihelion and aphelion (the times when the Earth is closest to and furthest from the Sun),  changes to the timing of equinoxes and solistices called precession and changes to the angle of Earth’s rotational tilt, which varies from 21.5 to 24.5 degrees. When these cycles come into phase, say the Earth is at perihelion (or as close as it gets to the sun during its orbit) during an especially eccentric (or maximally elliptically shaped) orbit, at the same time as the summer solstice and when the tilt is at its 24.5 degrees, all three factors add up to maximize the amount of sun hitting the hemisphere experiencing summer. These cycles can amplify or dampen seasonal effects and in conjunction with other climate feedback systems can induce rapid climate shifts. For example, they are thought to play a role in the glacial advances and retreats of the past two million years. On a much, much smaller time frame, we know that regionally, the amount of sun reaching the Earth varies, we call this phenomenon the seasons. In the winter less sunlight is reaching us than in the summer. When we talk about global climate we average these variations out because in winter here, its summer some where else on Earth, but seasonal variation can influence climate, particularly when in conjunction with other climate change drivers. Mostly though we think of these variation as being averaged out.

So, in conclusion, it is possible for the output of the sun to vary, but the changes are either too miniscule or operate on too long a time scale to account for the totality of the observed changes to current global average temperatures. Next time we will look at the other independent components of the climate system, albedo, or reflectivity of the Earth, which influences how much energy is reflected away from Earth and therefore not available to enter the climate system at all, and the components of the climate system that absorb light and heat, influencing how that heat either escapes or recirculates in Earth’s atmosphere and oceans.

 

References:

Real Climate (website run by climate scientists) is an excellent source of timely and topical info and perspective by those in the thick of this research. Here is a post about solar forcing and how relevant it is (or isn’t): http://www.realclimate.org/index.php/archives/2005/07/the-lure-of-solar-forcing/

http://www.astro.cornell.edu/academics/courses/astro201/evol_sun.htm

Cute little slide show about Milankovich cycles: http://www.sciencecourseware.org/eec/GlobalWarming/Tutorials/Milankovitch/

Climate Change: Part 3 Earth Energy Balance

Note: This program first aired on March 15, 2014.

The first thing we need to understand about the Earth’s climate is that it is the result of a balance, what is called the energy balance. When the same amount of energy comes in that leaves, the system is in balance and the average temperature stays the same.  If more energy leaves the system than comes in, the net amount of energy decreases, and the system cools. If more energy comes into the system than leaves, energy builds up and the average temperature rises. Its like your household budget. If you spend more money than you make, your savings account gets smaller. If you save more than you spend, your savings account gets bigger. If you spend what you make each week, no more, no less, your savings account will stay the same.  Earth’s climate works the same way. For the past 10,000 years or so we’ve been in equilibrium, or balance. The energy in has equaled the energy out, and the overall average climate has been stable. We are in a situation now however where we are taking in more energy than we are giving out, and the climate is out of equilibrium. The temperature will shift until the system is back into equilibrium, in this case, it will warm until the inputs and outputs are back in balance.

Recall if you will the law of the conservation of energy: energy is neither created nor destroyed, but it can change form. What is the source of energy that comes to Earth? The source of the energy that Earth runs on is the Sun. The sun’s energy comes to us in the form of visible light. About 30% of that light is immediately reflected back away from Earth as light, and plays no part in the climate system. It bounces off clouds in the atmosphere as well as brightly reflective surfaces on Earth that have what is called a high albedo, or reflectivity, things like snow, ice, light colored desert. That energy that is reflected doesn’t change wavelength, it arrives as visible light and it leaves as visible light. The other roughly 70% of light however enters the Earth’s climate system by getting absorbed by the atmosphere and the surface of the Earth. After getting absorbed, it is reradiated back out as infrared radiation aka heat. Infrared radiation is a longer lower energy wave length, and is not visible to us, but we can feel it. For thermal equilibrium, the Earth would need to reradiate all 70% of that incoming energy back out. The lag time it takes between the light coming in, and the infrared going back out is what creates an average global temperature greater than absolute zero. While that infrared radiation is making its way back into space, its heating up rocks and water and air and gasses in the atmosphere, which then reradiate the infrared radiation back out again.

Of that 70% of the Sun’s energy that makes it into the climate system, 23% is absorbed by the atmosphere. When that energy is reradiated back out, it goes in all directions, some back into space, some towards Earth. The Earth’s surface absorbs the other 48% of energy directly from the Sun (23+48 = 71, or the about 70 % total). A great deal of that energy actually goes into non sensible heat operations. The first and largest is evaporation. Water absorbs the light energy, but since water has such a high specific heat, it takes a lot of energy before the water actually changes temperature. 25% of that energy hitting Earth goes into simply evaporating water. Heat is still moved, in fact evaporation is major component of moving heat around the climate system, but its not like we feel it like we do when we stand next to the woodstove. The next 5% is moved via convection. The heat is moved not by radiation but physically by air warmed by contact with the warm surface of the Earth. The air rises into the atmosphere taking the heat with it. Its only the last 17% that actually gets reradiated back towards space as infrared radiation, and this is where the tally sheet doesn’t balance. Of that 17%, only 12 ultimately makes it back into space. The remaining 5% is left to build up here in the climate system. And when not everything that comes in makes it back out, we have a system out of equilibrium. The only way for a system to get back into equilibrium is for it to shift. That’s what’s going on now.

Next week we’ll take a look at how the pieces of the climate system work together, and why heat is building up here on Earth.

References:

Your tax dollars at work: The NASA Earth Observatory website is a wealth of great earth and sky science. This page on the Energy Budget is very helpful and full of details I couldn’t cover here: http://earthobservatory.nasa.gov/Features/EnergyBalance/

Climate Change: Part 2 How Science Works

Note: This program first aired March 8, 2014.

It’s the nearing the end of winter (we hope), and most of us in North America are sick of the cold, I know I certainly am, and I love winter! Taken in this context, a warmer climate doesn’t sound that bad. Maybe you or some one you know has even questioned how “global warming” (as it is called in the popular literature) can be real if we are having such a cold, hard core winter. Actually, global warming is a misnomer. The warming part refers to the increase in mean or average global surface temperatures, but that is just an average. We can average both 0 plus 10, and 4 plus 6 and get 5 each time. The range between 0 and 10 is much greater than the range between 4 and 6 yet both data pairs tell us the same story when averaged together. Averages are necessary when looking at climate, because climate is a global phenomenon, the result of a global system. The Earth has warmed approximately 0.7 degrees C (or 1.25 degrees F) in the past 100 years. But don’t let the average warming lull you into the dream of the end of winter, while its likely that winters may be getting milder, more heat in the climate system ultimately means more instability, and more chaos in weather patterns. This instability can mean things like what happened this winter, with the polar vortex wandering south, are also likely.

At least if you are questioning the veracity of climate change this winter, you are doing so based on evidence, the evidence being its cold! How can this be a sign of global warming? I applaud you for looking around and actually observing what is happening in the world around you, and making connections to things you have heard are supposed to be happening. The problem is, climate isn’t quite that simple and as a result, we shouldn’t really be calling it global warming. The phenomenon is global in scale, and most of us operate on a human sized scale of observation. So where you are at any give moment (or many many moments this winter), may seem colder than usual, that doesn’t mean that on average, Earth isn’t warming up, it is.

The hardest conversations to have are those with people who don’t “believe” in climate change. Not believing in climate change is sort of like not believing in gravity. Its not believing in how science explains things in the world. Not believing in how science works is always a choice, but people need to understand the implications of that choice. Science seeks to explain natural phenomena through observing, collecting evidence, testing and establishing attribution or cause and effect.

Sometimes science misses the truth because it isn’t asking the right questions, or asking enough questions. That isn’t the case this time around. There are so many scientists working so hard on this issue, from so many different angles; we’re not missing any big picture components. There is so much evidence that has been documented, about how the climate system works, what makes is shift, how it shifts, how fast it shifts. There is a lot we don’t know in this exciting field of inquiry, but the big picture mechanisms of the climate system are well established.

So do me a favor, and when you want to have a conversation about climate change, don’t start it with anything having to do with belief. While there are philosophical discussions to be had about any topic, including climate change, whether or not it is happening and whether or not it is being caused by our carbon dioxide emissions is a question for science. If you want to deny climate change, you need to do so based on evidence, and good luck with that, because the evidence is pretty overwhelming! And by evidence I don’t mean what the talking heads on CNN or NPR or Fox News or some nutty lady on community radio says. Get as close as you can to the source, the people doing the investigating. They are the ones in the trenches, looking at this day in and day out. And I’ll tell you, they are pretty alarmed with what they are learning.

We’ll look more at the climate system and what scientists are finding so alarming in the coming weeks.

 

References:

Andy Borowitz’s great post on Climate change and the winter that wouldn’t quit being so hardcore: http://www.newyorker.com/online/blogs/borowitzreport/2014/01/polar-vortex-causes-hundreds-of-injuries-as-people-making-snide-remarks-about-climate-change-are-pun.html

There is SO MUCH information out there on the web about climate change, but some of the nicest and most concise is from NASA’s Earth Observatory: http://earthobservatory.nasa.gov/Features/GlobalWarming/page1.php

Climate Change: Part 1 Introduction

Note: This program first aired March 1, 2014.

Its time for another series here on the World Around Us, so the next big thing we’re going to spend a few weeks talking about is something that is happening to the world around us. That big thing has the potential to change where a billion of us live, where and how we grow our food, where it rains and where it doesn’t, how ocean currents circulate around the globe, or not, what can even live in the ocean. In short, this phenomenon stands to transform the world beyond the experience of any of us, of any human being that has ever lived. I’m talking of course about climate change, and we’ll spend the next several weeks looking in detail at science behind this multi faceted phenomenon.

Climate change simply refers to a change in the overall global average temperature and the associated shifts in weather patterns that accompany the change. The Earth’s climate has changed many, many times over the course of Earth’s history, generating climates both colder and warmer than what we experience, on average on Earth today. These shifts typically take thousands of years. There are various reasons the climate changes, for example the intensity of the sun has changed over time, the Earth’s orbit and thus distance from the sun varies, the processes of plate tectonics move the continents around which changes ocean and atmospheric circulation and thus heat distribution patterns, the composition of the atmosphere has changed, climate has even been effect by extra terrestrial objects. For the past 2 million years, the Earth has experienced, not a steady temperature, but a consistent pattern of alternating average temperatures, with cooler periods that resulted in long stretches of glaciation in the northern hemisphere, alternating with warmer periods, during which time the glaciation receded. We’re in one of those warmer in between glacial periods now. But instead of cooling back off and plunging the northern hemisphere back into ice, evidence points to a small increase in average temperature having occurred already, and puts us on the brink of larger increases in the near future. We are perhaps leaving this ice age pattern and moving into a different climate regime.

It should be clear then, that climate change is a normal occurrence on Earth. What is all the fuss about then? Because, just as we have loads of evidence about how climate has changed in the past 500 million or more years, we also have loads of evidence about what the consequences of those climate changes have been. What we find is that rapid and dramatic climate change represents an existential crisis for most living organisms. Rapid changes in climate often accompany mass extinction events, when 60, 70, 80, 90% of families of organisms disappear from the fossil record. So that dear listeners, is the thing to be worried about. If you like how things are on this planet currently, be aware, things are likely to change, not quite on the time scale of your life, but possibly not too much longer than that. The processes of evolution have done an amazing job of repopulating the Earth after these mass extinction events, in fact evolution seems to happen most rapidly when the physical environment changes. Knowing that, I have no doubt that life on Earth will go on and even flourish. No, climate change is ultimately an existential crisis for us. Humans have evolved in a very narrow window of relative climate stability, and all of what we would call the development of agriculture and modern civilization has occurred in this briefest of moments in this interglacial period. As far as we know biologically, its only ever been about this warm, or colder, in our evolutionary period. Its never been warmer, and warmer is where it appears we are going, fast. While the Earth has certainly been there before, we never have, and that reality could have serious consequences.

Join us in the coming weeks as we attempt to explain the science of what is happening, how we know what we know, where all this might be headed and what we can do about it. It’s a topic laden with emotion, political and economic baggage but I think you will find, the science is fascinating. From that point of view, we are truly living in interesting times.