our planet has been draped in ice sheets filled with boiling hot oceans and dimmed by volcanic ash all before anything more complicated than a single-celled organism showed up so climate change is nothing new around here when it happens gradually over millions of years but something new has happened in the last few centuries People Like Us except wearing hats like this began burning fossil fuels like coal oil and natural gas to make energy most of us aren't wearing hats like those anymore but we're still powering our daily lives and industries with those fuels releasing billions of
tons of carbon dioxide every year and that's caused earth's climate to change in the span of just a few human lifetimes the geological blink of an eye hi I'm Dr Sammy your friendly neighborhood entomologist and this is Crash Course biology hey do you guys smell that smells like same music [Music] now I know what you're thinking wait is isn't this crash course biology and yeah this episode is heavy on the gases low on the Golgi bodies and that might leave you wondering what does climate change have to do with the signs of Life here's the
thing life and climate are tied together like that Tangled pair of headphones at the bottom of your backpack you know like you you tug one end and then a knot tightens which is looked around a paper clip somehow snagged on that tiny notebook where he drew Hearts around your crush's name which after several drugs is now lying open on the floor and I'm breaking a new cool switch thinking about it um but back to the point we can't talk about life without talking about climate which doesn't mean last week's thunderstorm or or a one-day temperature
swing that's weather climate is long-term weather conditions averaged over many years to understand the difference between them just remember that knowing the weather will help you decide if you should grab an umbrella before you head out but knowing the climate will help you decide if you should invest in a good air conditioner while the weather might impact your choice of clothing for the day the climate directly impacts wear and when different kinds of Life can survive we owe today's climate to the fact that our little green and blue marble of a home isn't just floating
in space unprotected it's wrapped up in an atmosphere a big invisible gassy jacket which granted sounds pretty weird when you put it that way but without it we wouldn't exist this jacket is made of different kinds of gases and a small fraction of them known as greenhouse gases absorb solar energy like super well we're talking about gases like methane water vapor and most importantly carbon dioxide also known as CO2 they account for less than half of one percent of our atmospheric jacket but they're a part of what makes it so good at trapping heat sort
of like all the little white feathers in your puffy coat when sunlight beams down from space most of it travels through those gases with no problem the energy from that sunlight gets absorbed as it strikes the Earth warming the surface that type of warming is normal and seasonal the Earth naturally bounces some of that solar energy back towards space where some of it exits the atmosphere and heads right back out into the inky ether but the rest of that energy gets trapped by the Earth's gassy jacket specifically by those super absorbent greenhouse gases which suck
up heat and bounce it back down to us again this warming process is called the greenhouse effect unsurprisingly it works the same way as a greenhouse using layers of glass to trap heat inside and it keeps Earth at a nice cozy insulated average of 14 degrees Celsius without it our Earth would be a chilly average temperature of negative 18 degrees Celsius great for storing ice cream the rainforests swimsuits or us for that matter so the greenhouse effect is a natural healthful process that makes Earth habitable for all of life but you can have too much
of a good thing when our atmospheric jacket contains more carbon dioxide for example it gets really good at trapping heat like too good and the hotter things get the more water evaporates and joins the atmosphere and remember water vapor itself is a greenhouse gas so that in turn absorbs even more heat creating a looping system of cause and effect that just keeps reinforcing itself and while dressing in layers is great if you're hiking in the Alps it's really hard for our planet to shed its extra coats so all of that heat gets stuck going from
the ground to the atmosphere like the worst game of hot potato ever played when I learned about this I was like wow what a revelation I can't believe we've only recently figured this out but it turns out that this isn't new knowledge we've known how and why this could happen for nearly 170 years let's pay a visit to the theater of life back in 1856 Eunice foot an American scientist and suffragette was thinking about how the sun's warmth affected different gases in those days the scientific Community was a bit like a fort with a handmade
no girls allowed sign out front but foot wasn't deterred and ran her experiments anyway she filled tubes with different combinations of gases including carbon dioxide after putting some tubes in the Sun and some in the shade she compared their temperatures trying to find the hottest gas all the tubes in direct sunlight warmed up but none as intensely as the tube that contained carbon dioxide the temperature had soared to 51.7 degrees Celsius hot enough to burn your fingers from that Insight foot theorized that if our atmosphere ever contained more carbon dioxide the whole planet would warm
up as a result which would mean a lot more than a few slided fingers and sure enough today that's exactly the situation we're in foot was one of the first scientists to recognize carbon dioxide's potential to affect earth's climate but she wasn't the only one to connect the dots for example just a few decades later another scientist named Dr cevante arenius observes that burning coal releases carbon dioxide as a fossil fuel coal forms from the decomposed carbon-based bodies of plants and animals that lived and died a long time ago and I'm talking before the dinosaurs
so no I'm afraid that means you aren't gassing up your car with the remains of a T-Rex when we burn those fossil fuels whether it's in the form of coal oil or natural gas carbon dioxide gets released into the atmosphere when Arenas ran the numbers he predicted that carbon dioxide released by burning fossil fuels could warm our climate within a few thousand years if we kept burning them at their current rate but we far outpaced his estimates our emissions of carbon dioxide have grown and grown and grown and so has the mountain of evidence that
those emissions are warming our planet some oil and gas companies have worked to promote uncertainty around the existence of climate change and what's causing it while they have only very recently acknowledged its existence as of 2023 they're still trying to deflect from what's causing it but the scientific consensus on this is overwhelming you can learn much more about that in our climate and energy series we've only been reliably taking direct measurements of Earth's Global temperature since the 19th century but at measly slice of Time Shows a steady rise in temperature of a about 1.1 degrees
Celsius since 1880 and we know that that's unusual because we've learned to read Earth's much longer climate diary in the form of ice cores see when snow hardens into ice Tiny Bubbles of air remain trapped in the gaps between snowflakes these gases and water molecules stay frozen like entries in a frosty Journal so by drilling deep down into Polar Ice we can snoop on what the atmosphere was like hundreds of thousands of years ago ice cores show us that carbon dioxide levels have fluctuated over the past 800 000 years and and temperatures have fallen and
risen alongside them too but when people started burning fossil fuels carbon dioxide levels began to spike quickly like really really quickly and they haven't stopped Rising before the Industrial Revolution for every million molecules of air in our atmosphere around 280 were carbon dioxide molecules but by 2022 the number had increased to 422 the highest concentration of carbon dioxide our planet is seen in 4 million years and that's surge in carbon dioxide affects more than just the temperature as the amount of carbon dioxide in our atmosphere Rises it impacts all of Earth's systems like yanking on
the end of that Tangled mess of headphones impacted all of the other items in my bag and eventually everybody around us when stuff started falling out it's all connected is what I'm saying for example the ocean is our planet's largest carbon sink it's sort of like a big storage container for carbon in fact the ocean holds 50 times more carbon than the air or soil do but a chemical reaction happens when carbon dioxide meets water it creates an acid so that influx of carbon has already turned the ocean 30 percent more acidic since the 19th
century as carbon dioxide and other greenhouse gases trap more heat there's more energy pouring into our planet than going out that means more energy is pumped into the ocean fueling hurricanes and and typhoons to become more frequent and more intense as the whole planet gets hotter that triggers all kinds of changes spring arrives earlier leading to Shorter Winters and longer summers Rising temperatures lead to double whammy droughts and heat waves and that leaves Forest floors full of dried up plants that serve as fuel for wildfires to ignite spreading faster farther and more often plus Earth's
polar ice caps are melting transforming solid ice to slush and sea water and that's causing ocean levels to rise and encroach on land so while some communities are already facing a problem of not enough water others are facing a problem of too much and because these adverse changes layer on top of existing social inequalities they disproportionately affect lower income communities and people of color making climate change not only a scientific issue but a matter of environmental justice that has spurred some researchers to political action for example climate scientist Nicole Hernandez Hammer witnessed firsthand through her
field research the sea level rise alongside Miami Beach's Latino communities but these communities were not included in conversations about climate change or the dangers of rising sea levels so hammer took action moving into environmental Outreach and education and while the threat is still there these communities are now in conversation about climate change and able to plan and advocate for the future of their environment and the good news more broadly is we know exactly why these Tangled complex effects are happening the more we burn those fossil fuels the more greenhouse gases we release and that's driving
sweeping changes all over our planet and these changes are impacting life at all levels from the tiniest bacterium to the elephants of Botswana to you and me we can slow these impacts by breaking up with fossil fuels but we also have to invest in Nature's carbon sinks such as soils and forests Which pull carbon out of the atmosphere and back into the land where it can't keep heating things up it won't be the easiest breakup we've designed whole societies and Global Systems around fossil fuels we should fully expect to be listening to Jasmine Sullivan on
repeat with a gallon of rocky road but this is one relationship we can't afford to stay in so in order to hold emissions we have to both invent new systems and work more efficiently within old ones and to do that we've got to get a whole planet's worth of people on board and if you've ever been part of a group project you know that last part isn't easy thankfully when faced with global crises humans have one great thing going for us we are creative I mean we've been to space we've we've got electric cars we
made Furbies for some reason and so yes it's going to take all of our creativity and cooperation to tackle but the only way through in the only way through is together in our next episode we'll tune back into the world of living things and see how our rapidly changing climate involves much more than the atmosphere it affects every living breathing organism on this planet including you and me this series was produced in collaboration with hhmi biointeractive if you're an educator visit biointeractive.org crash course for classroom resources and professional development related to the topics covered in
this course thanks for watching this episode of Crash Course biology which was filmed in our studio in Indianapolis Indiana and was made with the help of olive fees nice people if you want to help keep crash course free for everyone or ever you can join our community on patreon [Music]
