A series on this channel talking about the environment without focusing on the era-defining
change happening to our planet right now wouldn’t make any sense.
Climate Change is after all, the hot mess we all find ourselves in.
Climate is the long-term, average weather over a particular region.
It’s the typical patterns of temperature, precipitation, wind and how those change seasonally
throughout the year.
But what does that actually mean?
Let’s take a trip to a few biomes and compare what climate looks like around the world.
We’re going to the tropical rainforest of Brazil, the savanna of Mozambique, the desert
in Saudi Arabia, and the tundra of Canada.
Now, the daily weather might change a lot in these biomes, depending on the day, the
Candaian tundra could be hotter than the desert, but what we’re interested in is the climate.
A useful tool for comparing climates like these are climatograms, which visually represent
the climate of a region throughout time.
This gives us not only an idea of what the climate is, how much rain and how warm, but
also, the seasonal patterns.
On average, the desert and the tundra are both very dry, without much rainfall, but
a desert is hotter than the tundra.
Tropical rainforests and savannas are both hot, but you’ll see a lot more precipitation
in the Brazilian rainforest than this savanna.
Clearly, climates vary widely, from the frigid, dry tundra to the hot and humid rainforests,
but what causes all these different regional climates?
As Joe mentioned in the first episode of this series, terrestrial biomes are defined by
their temperature and precipitation - basically their climate.
And the main driver of temperature on this planet?
That’d be the sun.
Now, if our planet wasn’t more or less spherical, and was like a flat sheet, everywhere on earth
would experience the same solar insolation.
Solar insolation is the amount of heat energy from the sun, or solar radiation, that hits
an area.
But, because Earth is a sphere, solar energy from the sun hits different parts of the globe
at different angles.
The equator is so warm because the incoming solar radiation is perpendicular to the surface.
Up at the poles that angle is more oblique.
The sun is emitting the same amount of heat energy, but in the equator that energy is
more concentrated while at the poles it's more spread out.
Imagine shining a flashlight on a basketball.
Near the middle, the light from the flashlight is a perfect circle, but as you move the flashflight
up it becomes more oblong.
This unequal heating of the Earth’s surface causes the difference in temperature, but
it also drives much of the global climate.
Because sunlight doesn’t just heat the ground, it also heats the air.
When heated, the molecules of air expand, becoming less dense and rise.
As those molecules get higher up in the atmosphere they begin to cool down, become denser again
and sink.
These rising and falling air masses create global wind patterns that act like enormous
conveyor belts, transporting not just heat but also moisture all over the planet.
Warm air holds more water vapor and cooler air holds less.
This is because warmer air molecules have more energy and move around more
so the water vapor can't condense out.
As that air rises, cools, and becomes less energized, suddenly the colliding water molecules
can condense instead of bouncing off each other,
changing from water vapor into liquid water droplets.
And that often means precipitation like rain or snow.
The heat energy from the sun spread unevenly across the planet drives wind patterns and
the hydrologic cycle.
And all together, these cycles of wind, rain, and heat form the basis for the variety of
climate patterns on Earth.
The sun, and unequal solar insolation on the surface, drives the entire climate system,
but, the sun alone doesn’t make all this work.
The earth also has a kind of ‘blanket’ of molecules that trap some of the sun’s
heat, and without it, all that solar insolation would hit the earth and then head right back
into space.
This blanket is the greenhouse effect.
And it is what makes our planet liveable.
Without it, Earth’s temperatures would swing wildly, more like Mars or the Moon, with freezing
cold nights and warm to blazing hot days.
The greenhouse effect gets its name from, well, greenhouses.
Greenhouses are great places to grow plants, all year long, because they trap the sun’s
heat.
The transparent glass or plastic of a greenhouse roof lets in sunlight, warming the air and
the plants and the everything inside.
But, when that heat energy tries to leave the greenhouse a lot of it is reflected back
inside.
The greenhouse gases in the atmosphere do basically the same thing.
Incoming solar radiation - heat energy from the sun - heads toward the earth.
A lot of this energy is absorbed by the ground, water, trees, warming everything up.
Some of it is reflected by the atmosphere and clouds, or other objects at the surface
with high albedo, or reflectiveness, like glaciers, and heads back out into space.
Where things really start to warm up, and greenhouse gases get involved, is when an
object, like a road or a lake, absorbs all that heat from the sun and it starts to give
off heat of its own.
Which is why walking across pavement without shoes on can be a painful experience in the
summer.
Compared to the energy from the sun, that re-emitted heat has a longer wavelength, in
the infrared of the light spectrum.
And when any of that infrared, re-emitted energy hits a greenhouse gas molecule, that
molecule is able to absorb that energy and re-radiate it, warming the atmosphere.
Like a real-greenhouse’s windows, greenhouse gases are like a big blanket or jacket, wrapping
the earth keeping heat trapped inside.
The greenhouse gas molecules in the atmosphere play a critical role in regulating the temperature
of our planet.
Keeping things fairly stable, without massive temperature shifts between scorching days
and frigid nights.
But, it is a balanced system.
Too few greenhouse gases in the atmosphere and things start to get a bit chilly, and
when we add additional greenhouse gases, we’re making the planet warmer.
Climate change happens when the balance of greenhouse gases is thrown out of whack.
Which means, if we, and the rest of the organisms on the planet, want to live as we do now,
then we should be concerned about the amount of greenhouse gases in the atmosphere.
Just to make this crystal clear: the higher the concentration of greenhouse gases there
are in the atmosphere, the more heat will be trapped and the greater the overall global
temperature.
Now that you know what greenhouse gases do, let’s talk about what greenhouse gases are.
There are a lot of different greenhouse gases, because this umbrella term includes any molecules
that absorb outgoing long-wave radiation from the earth.
But some play a bigger role than others - so we’re only going to focus on three: carbon
dioxide, methane, and nitrous oxide.
These aren’t the molecules that trap the most overall heat: that’d be water vapor,
or the most heat per molecule: sulfur hexafluoride earns that title.
These are the greenhouse gases that humans are adding lots of and are causing the most
overall warming.
Let’s start with carbon dioxide.
Perhaps the most infamous of the bunch.
Let’s look at a graph of paleoclimate that reaches way back into geologic history.
This data behind this chart comes from ice cores, because trapped in long-ago frozen
ice are tiny bubbles of air that still look like the atmosphere when they froze.
You can probably see a pattern here.
When global temperature is low, CO2 in the atmosphere is low, when the global temperature
is high, CO2 in the atmosphere is high.
Even without doing any analysis of the actual numbers, we can see that temperature and CO2
concentrations are correlated.
We can also see that there is a cyclical pattern, and that the highs and low points have been
roughly the same as far back as this model goes.
These long-term cyclical patterns show the natural fluctuations of temperature and carbon
dioxide, caused by things like the slowly shifting tilt and orbit of the earth.
And when I say slowly, I mean really slowly.
Look at the horizontal x-axis on this chart.
The distance between the peaks is hundreds of thousands of years - a length of time so
long that I personally have no frame of reference for.
Now, take a look at the end of this graph.
Carbon dioxide spikes up, way higher than we’ve ever seen in the ice-core records.
We talked about this chart in the episode on the atmosphere, but this is the Keeling
curve.
A daily-record of carbon dioxide concentration at Mauna Loa, Hawaii since 1958.
There’s two distinct trends here: the small yearly fluctuations and an overall trend upward.
Those yearly fluctuations are because of less photosynthesis, and therefore less drawdown
of CO2, occurring during the northern hemisphere winter months.
The northern hemisphere has more land mass, so the seasonal cycle of trees and grasses
has an impact on global carbon dioxide concentrations.
During the northern hemisphere summer, when all the plants wake up, photosynthesis rates
go up, plants drawdown carbon dioxide out of the air and transform it into organic compounds.
The yearly cycle is natural, and expected, and has probably been going on for millennia
- it is that upward trend that is worth worrying about.
And if you look at the numbers, the increasing carbon dioxide concentration is exponential,
with the rate of increase growing every year.
This exponential increase is because of humans, caused largely by deforestation, and by burning
fossil fuels - for heating, transportation, industrial uses, and electricity.
Deforestation is a double whammy emissions-wise because forests serve as a carbon sink.
Trees sequester carbon in their tissues, trapping it for a very long time.
Not only does cutting down those trees end up releasing that stored carbon, but it also
means fewer old-growth trees to sequester the carbon dioxide in the atmosphere.
Reducing fossil fuel use and deforestation is essential to reducing carbon dioxide concentration
in the atmosphere and slowing future warming.
Alright, now let’s talk about methane.
Methane has some naturally occurring sources, like wetlands, but human emissions primarily
come from landfills, raising cattle, and the gas industry.
At a landfill, the organic material buried inside all of that trash starts to decompose
in anaerobic - or oxygen free - environments.
Cattle produce methane as part of their digestive process, and with millions of farmed cattle
on Earth, those cow burps make up a major methane source.
And mining, transportation, and use of liquified natural gas (which is mainly methane) are
also serious sources.
Finally, we have nitrous oxide.
Technically laughing gas, but definitely not funny.
This greenhouse gas is generated as a by-product of fertilizer on agricultural fields.
Nitrogen is one of the limiting factors in most soils, regulating how many plants can
grow.
To increase the yield, and to maintain soil fertility, farmers add nitrogen to their fields.
While that helps the plants grow, bacteria in those fields convert that nitrogen into
nitrous oxide.
The more fertilizer used, the more nitrous oxide emissions.
Even though it is well understood that increased greenhouse gases cause climate change, emissions
of all of these greenhouse gases, carbon dioxide, methane, and nitrous oxide are still rising.
Which is… not great.
But why, what does increased greenhouse gases and the resulting climate change actually
mean for humans and the environment?
Well the obvious - it will get hotter.
And it has, the global average temperature has already increased more than 1 degrees
Celsius since the 1800s.
But that’s just the global average, some places are getting warmer faster - like the
poles.
And temperatures going up alone isn’t the issue, because the planet warming up also
causes changes in the climate.
At different temperatures molecules in the air and ocean behave differently, so as things
heat up, we see changes in wind patterns, precipitation, and ocean currents.
In some areas this means increased droughts and forest fires, in others, more frequent
floods and stronger hurricanes.
Devastating hazards aren’t the only impact of climate change though.
As parts of the planet become warmer, we also see habitats disappearing or shifting - with
dramatic consequences for the biosphere.
Every organism has a range of tolerance for abiotic factors, like salinity, pH, and temperature.
If those factors become too extreme, the organism has to move or die.
Some species have been moving their home ranges in response to changing temperature patterns.
For example, lobsters off the eastern coast of North America are shifting northward in
search of cooler waters.
But other species, where moving isn’t as ‘easy’ - like certain tree species - are
disappearing.
Climate change is also messing with the seasons.
Phenological spring, the time of year when plants start to bud new growth, has occurred
earlier in response to a warming planet.
For instance, researchers have tracked the date that cherry trees blossom in Japan based
on centuries of diary entries and chronicles.
After twelve hundred years of a nice steady cycle, the peak for cherry blossoms in Japan
has been getting earlier and earlier thanks to climate change.
The oceans are becoming warmer too.
And as you may remember from episode three - the oceans make up a huge portion of the
planet.
So increased temperatures in the oceans have ramifications all over.
The oceans are warming fastest at the surface, which leads to an increase in a thing called
ocean stratification.
Basically, the ocean, or really any mildly deep body of water has layers with distinct
temperature and light infiltration.
Because the surface water warms faster than those below this increases the distinction
between the upper layers of the ocean and lower layers.
Some stratification is normal and important for nutrient flow, but like most things, when
you turn the dial to 11, we start to see problems.
Like, less upwelling and nutrient mixing, which usually brings cold water full of nutrients
to the surface.
Without the flow of nutrient-rich deep water, ocean surface organisms can’t survive.
Phytoplankton - a broad category of microalgae that like to float around the surface - don’t
do super well without those nutrients.
Which would be bad on its own, because phytoplankton are an integral part of the marine food web
- acting like terrestrial plants converting energy from sunlight into their little bodies
- but phytoplankton are, through the sheer amount of photosynthesis they do, both a major
source of oxygen and pull literal tons of carbon dioxide out of the atmosphere.
Both things we humans rely on for a stable climate.
Increasing ocean temperatures also means rising sea levels.
Like the air, as water temperature increases, the energized water molecules take up more volume.
One drop of water expanding a tiny tiny bit doesn’t change much, but when you multiply
that by the immense volume of an ocean, from this thermal expansion alone, global average
sea level rises 1.4ish mm a year.
And increasing temperatures also melt ice.
Ice melt from land-based ice, like the greenland ice sheet, accounts for 1.8 mm a year of global
average sea level rise.
A few millimeters is admittedly very small, if you’re thinking about your local beach.
But this is average rise, so in some places ocean levels are rising faster.
And, it’s rising a few millimeters every single year, and that adds up.
This means by 2100 we could see more than a meter of sea level rise.
Which, again, might not sound like much, but when you consider the risk of storm surge
and coastal flooding, every extra centimeter puts coastal communities and millions of people
at risk.
Pumping carbon dioxide into the atmosphere doesn’t just raise ocean temperatures - it
also causes ocean acidification.
But all that extra CO2 in the ocean turns into carbonic acid and drops the pH of the
water, taking a normal part of the carbon cycle and supercharging it.
Shellfish and other organisms that construct their shells and skeletons out of calcium
carbonate, are literally dissolving away or having a hard time growing their shells in
the first place because of ocean acidification.
Of course, all the impacts of climate change on the biosphere affect humans because we
rely on their ecosystem services.
As we’ve talked about in previous episodes, the oceans, atmosphere, and soil provide the
backbone for the entirety of human society.
When climate change starts messing up those systems, we’re going to feel it.
Correction: We’re already are.
But who is ‘we’ here?
In theory, climate change is a global problem.
The average global temperature is increasing, but who feels the effects of that temperature
increase and all the ramifications from heat waves, to hurricanes, to flooding.
That isn’t evenly distributed.
Disproportionately the impacts of climate change fall on low income communities and
communities of color.
Wealthier, and often whiter, communities with more access to resources can in some ways,
buy themselves out of some of the worst impacts.
This inequity is called Environmental Injustice or Climate Injustice.
And if you want to learn more, we’ve made a whole playlist for you to watch.
So what’s to be done?
That’s the big question when it comes to climate change.
And unfortunately there isn’t a single answer.
The global climate is a massive interconnected system.
So we need big solutions, and we need solutions for everyone - not just folks with the biggest
paychecks.
Generally speaking, though, these solutions fall into two categories: adaptation and mitigation.
We can adapt systems and structures to the new and future climate systems.
In response to sea level rise, this means building flood barriers or moving homes and
businesses away from low lying coastal areas.
As temperatures rise, adaptive measures look like drought-tolerant crops, or cooling centers,
which are free, air-conditioned spaces for people to escape deadly heat.
Adaptation also means developing policy and governance structures to support people displaced
by sea level rise, or cyclones, or droughts.
Adaptation helps preserve human life and systems, by responding to the impacts of climate change,
but it doesn’t tackle the cause of climate change: emissions.
Mitigation strategies are solutions that decarbonize, or reduce greenhouse gas emissions, like replacing
coal and gas power plants with renewable power generation, developing public transportation
systems and decreasing vehicle miles, or reducing food waste.
Mitigation also includes strategies that increase carbon storage, like preserving old-growth
forests and protecting peatland.
We’re already experiencing the effects of climate change, so for many places, adaptation
strategies are necessary.
But alone, adaptation will not be able to protect everyone from ever increasing climate risk
A focus on mitigation efforts, and lots of them, in concert with adaptation strategies
is required to combat climate change.
Climate change and climate science are their own field of study, but hopefully this video
gives you a sense of how climate fits into the field of environmental science, from modeling
and basic research to its impact on ecosystems and ecosystem services, and even its own tangled
web of policy questions.
There’s a lot more to say about climate, but luckily you’re on a whole channel that
focuses on it.
So after you’re done with this series, we’ve got plenty more for you.
For now, thanks for watching, and we’ll see you next time for a look at energy.