this video is brought to you by Squarespace in 2006 researchers first detected a strange peak in the amount of methane in Earth's atmosphere a greenhouse gas more powerful than carbon dioxide while the scientific Community rushed to explain the sudden rise they found to their surprise that for once at least it didn't match any relative increase in human fossil fuel use it looked as if overnight a big new source of methane had simply turned on something happening on a a global scale but no one could determine what was actually causing it these methane spikes happen every 100,000 years or so and are usually an indication of an Ice Age termination event a rapid warming at the end of an ice age that within just a couple of decades transitions the planet from largely ice covered to The Climate that we experience today but the last one only happened 12,000 years ago at the end of the last glacial maximum so why are we seeing another rise in methane so soon and what is causing it and 16 years later as the peak continues to grow year on year are we on track for a major climate reversal this is a topic that I find absolutely fascinating it's rare we find such a predominant Smoking Gun of something happening on a global scale that we fundamentally don't understand that also isn't the result of our direct impact on the planet to answer the question of what is actually going on here we need to understand some of the history of the planet and its climate currently we're in the quaternary period spanning from about 2. 58 million years ago to the present day the quaternary period has broken into two different epochs the first is the pene epoch from about 2 and a half million years ago to 11,700 years ago and it was known for its cyclical ice ages where during glaciation periods vast ice sheets would expand to cover much of North America northern Europe and Asia then after several tens of thousands of years they would Retreat over just a few thousand years to a period of warmer Global Climate the pine also saw significant evolutionary developments and migrations for humans for instance Homo erectus emerged in the early Pine and the atomically analogous modern Homo Sapien appeared later in the epoch eventually colonizing most of the planet the pine also witnessed the megap foral extinctions where many large animals like Willy mammoths mastadons saber-tooth cats eventually went extinct this was partly due to human hunting pressures but it was thought mostly to be driven by the significant climate shifts that could have disrupted habitats and food sources in many of the megal fornal species as the planet transitioned into its second Epoch the holos we've had one yes what about second Epoch from about 12,000 years ago to the present day marks the most recent period where the glaciers retreated and the planet has seen relatively stable and warm climate conditions here's where the terminology gets I think a little bit confusing we are still technically in an ice age just an ice age where the glaciers don't cover as much of the planet as they can do we call this period an interglacial period 50 million years ago the planet was too hot for any ice to form at the poles so relative to that the Earth is definitely still in an ice age this most recent Hollen Epoch is significant for human history as the stable and comparatively warm climate allowed for the development of Agriculture and consequently the growth of large human settlements and complex societies culminating obviously in the creation of social media the transition that brought us from the holos scene and from all glacial to interglacial periods are called Ice Age termination events again we're still in the Ice Age yes it's confusing these termination events are typically made up of three distinct phases though exactly the demarcations between each phase kind of vary depending on what researcher you're actually talking to the first phase is called the deglacial onset its slow but steady increase in global temperatures marking the beginning of the end for the glacial period it usually lasts several tens of thousands of years this is often driven by changes to Earth orbit called milankovich Cycles these predominantly relate to how the Earth is angled or orbiting around the Sun starting with e centricity it describes the Earth's orbit around the Sun and measures how much the orbital path deviates from a A Perfect Circle this can vary from zero it's a perfect circle to around 0. 067 it's more of an oval or an ellipse currently the eccentricity is around 0.
017 so we are pretty circular in our orbital nature when the Earth's orbit is more elliptical though the difference in solar energy that the Earth receives called insulation which is a word I have to look up every single time I need it between the closest approach and the most distant approach can vary tremendously this effect has a periodicity of roughly 100,000 years and over the past 800,000 years for which we've got data from Ice records termination events have been pretty well aligned with this cycle leading to Major glacial to interglacial shifts approximately 100,000 years apart but actually we don't think that this particular factor is the predominant milankovich driver of a termination event as the Earth rotates around the Sun it is tilted at an angle of 23. 5° but over time this oscillates between approximately 22. 1 and about 24.
5 in a period of 41,000 years from minimum to maximum or about 82,000 years for a full oscillation from 21° all the way up and then all the way back down again when the Tilt is greater what this does is expose a larger polar region and means that it receives more solar radiation during the summer which can ultimately lead to to more rapid melting of the ice sheets this in turn can have various feedback effects on the global climate looking at these events over the last 800,000 years you can see there's a huge amount of correlation between when they occur and when we are triggered into an Ice Age termination event today the axial tilt is decreasing from its maximum value and is moving towards the lower end of the range which should in theory be reducing the amount of melting effects on the ice caps the final effect I want to talk about is procession the wobble of the Earth's axis and affects the timing of the seasons relative to the position of Earth's orbit around the sun this possession cycle operates on time scales of approximately 19,000 to 23,000 years and we again see pretty regular alignment between these occurrences and termination events it obviously isn't perfect though it seems to be a combination of all these factors working together that actually drive a termination event to start these three malanovic factors drive a feedback loop which further propagates warming of the planet as the ice begins to melt darker Ocean or land and surfaces are exposed these darker surfaces are better absorbers of sunlight which leads to further warming and more melting as the process continues the Earth enters a rapid warming period called full deglaciation with significant further ice melt and a corresponding rise in sea levels over a very short period usually over a matter of just decades this process is driven by the Rapid Release of greenhouse gases like CO2 and methane which were pre previously dissolved in cold oceans or in the Now Melting permafrost ice layers the release of these gases drives further warming accelerating the process and often driving reorganization and strengthening ocean currents which serve to distribute heat more evenly around the planet it's only after this second rapid heating phase that global temperatures begin to stabilize marking the onset of an interglacial period which is the period that we are in now these ice sheets will also stabilize and start to reduce their size and sea levels will broadly come into some level of equilibrium while the system is still influenced by continuing effects of increased greenhouse gases malanovic Cycles negative feedback loops begin to play a more substantial role for instance as temperatures increase the growth of vegetation in previously ice covered areas acts as a carbon sink absorbing CO2 out of the atmosphere over a longer time scale weathering processes on land can then start to draw down atmospheric CO2 and lock it away in sediments and deposits while it also equilibrates with the now warmer oceans all of which serve to stabilize CO2 and temperature levels in the atmosphere this is the phase we're in now the hallene the interglacial period so why as of 2006 have we started to see this huge methane increase that we would only typically usually see in deglaciation phases of an Ice Age termination event it has been just 12,000 years since the last one not the usual 100,000 years that we usually see between the two what is going on but first I have to thank today's sponsor Squarespace Squarespace is the reason why I am where I am today that sounds overly dramatic but it is absolutely true I launched my first company to help scientists start startups based on their scientific breakthroughs having an incredibly intuitive easy-to ouse website builder to build a strong brand to communicate a mission was a central piece of what made our teams differentiated and look like companies that were professional and ready for investment I built about 40 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boomed by the 1990s these levels had stabilized the 2006 finding ings prompted a wave of Investigation to find the source of why methane had suddenly started to increase again this it turns out is a reasonably difficult thing to do methane's a hydrocarbon and it's one of the principal components of natural gas methane is produced naturally in Wetlands oceans geological processes such as venting and obviously through other biological processes where usually cow farts get the majority of the blame methane typically remains in the atmosphere for about a decade at a time before it is broken down predominantly by hydroxy radicals to form CO2 and water while there is a much shorter lifetime for methane by comparison to something like CO2 it has a much higher warming potential for a couple of reasons methane's bonds and its structure are very effective at absorbing and emitting infrared radiation heat specifically at about 3. 5 and 8 microns wavelength that 3.
5 and 8 Micron band is also in an atmospheric window that usually can make its way freely out to space whereas CO2 absorbs around the 4 Micron and 15 Micron waveband which the atmosphere already absorbs effectively this makes methane's contribution to the greenhouse effect much more pronounced in the past few years we've become significantly better at detecting where methane is actually coming from both from the ground and from space as in measuring it from satellites not leaks from space there are a few ways of doing this passively and active approaches but one that I want to talk about that I think is particularly interesting is by firing a laser ER at the ground if you pick a wavelength of laser that's either 3.
