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Thanks to human activity, the average global temperature has risen about one degree Celsius since the 1800s. And although that number is going up, if all goes well, we will be able to stop warming at about two degrees.

At least, that's the goal of agreements like the Paris Climate Accord. You hear this “two degrees” figure thrown around all the time on the news, and reporters often seem really concerned about it. Honestly, though, two degrees doesn't feel like a very big deal.

If that's the future we are headed toward, it seems like life might just be a little sweatier. The important thing for Americans to remember here is that 2 degrees Celsius is 3.6 degrees Fahrenheit. I know that it's not a big difference, but I do wanna be specific that we're talking about Celsius.

But, yes, 3.6 degrees Fahrenheit still doesn't seem like a ton, but despite how that number looks, there are big projections out there that show how a world only two degrees C warmer would be one that is much different than the world we live in today. So, even if we meet our goals, here's what we can expect. The first thing to know is this: A two-degree-Celsius difference isn't just the difference between a 26- and a 28-degree day in your hometown.

It's an average change to global temperature. So it's not like every place on Earth will warm exactly two degrees. Some places will be much hotter, some will have similar temperatures to today, and some will maybe even be a little cooler.

That means predictions for every city look different. But to give you a sense of what life might actually be like, let's zoom in on what the future holds for two very different places:. Vancouver, Canada, and Kolkata, India.

These cities are opposites in a million ways. Vancouver is, like, the epitome of the Pacific Northwest, with cold and rainy winters, and mild and sorta drier summers. It's got big pine trees, a big shipping port and a harbor, and big mountains nearby, where the winter Olympics were held in 2010.

And right now, the Vancouver area is home to about 2.5 million people. Kolkata, on the other hand, is nearly tropical. It's hot and muggy all year, especially in the late summer, when the monsoon rains come from the Indian Ocean.

Kolkata sits on the eastern bank of the Hooghly River, and it's an important industrial city and tech center. More than 14 million people live in the metro area, and the city is also the middle of a vast and super important agricultural region that grows rice, potatoes, sugar, wheat, and lots more. Both of these cities have a lot going on, and they both have a lot at stake in a warming world.

And the warmer part is really gonna be a problem for places like Kolkata. In a world that averages two degrees warmer, hot days will be a little hotter, cool days will be a little less cool. Heat waves, which are two or more extra hot days in a row, will be really common all over the globe, and scientists estimate they will affect something like 40 percent of the human population.

The waves will be even worse in places where there are big swaths of land with little vegetation, too. That's because land warms more easily than water, and because the concrete jungles of urban areas trap heat more than rural areas. So places like northern and southern Africa are gonna be extra vulnerable to heat waves, along with most of Europe, the Middle East, and a big swath of the eastern United States.

In hot and humid cities, like Kolkata, conditions become deadly when the temperature and humidity keeps the human body from being able to sweat out extra heat. So people working outside and those without air conditioning, millions in Kolkata alone, are super vulnerable to heat waves. And they're already happening more and more frequently.

In 2015, Southern Asia experienced a terrible one where 3500 people died just from the heat. And similar, but slightly less awful, waves happened in 1998, 2003, and 2010. So it's likely we will see more events like that in the future.

To cope with all of this, Kolkata might try incorporating more green spaces and green roofs, which would help dissipate some of the heat. They might also strengthen the fragile electricity system, that's important for air conditioning, and install more solar panels, which put less stress on the electricity infrastructure. So, in those respects, maybe the city will look different in a few decades.

It's hard to say. Meanwhile, in Vancouver, the higher temperatures won't necessarily be deadly, but they will still be a problem. See, Vancouver gets its drinking water from the nearby mountains.

The water comes from snow that falls on the mountain peaks and then melts in the spring and summer. But warmer temperatures mean more water is rain rather than snow. Based on well-tested models, the City of Vancouver projects that by 2080, because of warming air and ocean temperatures, they will have only about 15 percent of their traditional snowpack; that's how much snow is on the ground in the spring when melting starts.

So water shortages could really be a thing. And that would have a huge impact on everyday life. And it would also have a ripple effect throughout the economy, since water plays a big role in agriculture and certain types of manufacturing.

But the loss of the snowpack itself also comes with another major change to life in Vancouver: the possible loss of the ski season. Ski areas like Whistler-Blackcomb are the main tourist draws in winter, and they bring some 950 million Canadian dollars to the economy every year. Like you'd guess, these areas plan everything around how much snow they get.

But the IPCC, or the Intergovernmental Panel on Climate Change, projects that as the planet warms, the snow season will shorten by at least five days per decade, meaning that less snow will fall and temperatures will make it harder to make artificial snow. So by 2100, the ski season at Whistler will be a full month shorter. So shred that gnar while you can, man.

When it comes to climate change, the heat itself is the most obvious new thing we'll have to deal with. But rising temperatures also have secondary consequences. Like, all that heat tends to melt ice.

Mountain glaciers around the world are already on the retreat, the Greenland ice sheet is probably already starting a long, irreversible decline, although it's hard to say for sure, since humans have never experienced warming like this before. Meanwhile, West Antarctica will probably lose all of its ice shelves: glaciers that flow onto the ocean's surface and float there. It's already losing a lot of ice, and the rate seems to be accelerating every year.

Those losses will change the way the surface of our planet looks; we will have to start redrawing maps. But dumping cold water into the oceans has consequences for individual communities, too. The IPCC expects that by 2100, the average sea level will have risen about 50 centimeters.

That's enough to flood some of the world's biggest coastal cities, like Shanghai, Lagos, Jakarta, and many, many others. Even if cities aren't completely flooded, that doesn't mean they will escape the damage. For example, the City of Vancouver is expecting sea level rise anywhere from 30 centimeters to one meter by 2100, depending on what happens with ice melt.

That's not enough to put the whole city underwater, but it does mean that during storms and high tides, huge areas would be completely flooded. The famous Stanley Park in northwest Vancouver would become an island, and the industrial waterfront along Fraser River, including the central bus transit center, would be flooded. And although Kolkata is about 60 kilometers inland from the Bay of Bengal, people there will also feel the effects of a higher sea level, especially when storms hit.

Some parts of the city will flood more easily and more frequently. The Behala district, one of the oldest residential areas, and the Salt Lake area are particularly vulnerable. Plus, the Bay of Bengal is ringed by low islands called the Sundarbans and the world's biggest population of endangered Royal Bengal tigers lives there, plus an incredible and unique forest ecosystem, and four-and-a-half million people.

In fact, the sea is already creeping up on these islands, and more than a million people have moved from those islands to Kolkata so far. And as the sea level continues to rise, more will have to move, and more forest will be lost. So, even if we meet our two-degree goal, we'll be dealing with heat waves and flooding.

But in the news, you might have also heard about extreme weather. Well, we'll probably have to deal with that, too. See, adding all that water from ice melt doesn't just affect sea level:.

It also affects ocean circulation, especially in the North Atlantic where Greenland's meltwater goes. Ocean circulation is driven by changes in water temperature and salinity, or saltiness. In the North Atlantic Ocean, salty, dense water from the tropics cools down and gets even more dense, causing it to sink.

And this sinking forces colder, less dense water to rise to the surface. The whole process is called overturning circulation, and it plays a major role in the water's temperature. But a melting Greenland would mess up that process.

As ice melts and the cold, fresh water drains into the ocean, it makes that tropical water less salty and, therefore, less dense. And that means it'll be less likely to sink and overturn. Scientists have already observed a slight slowdown of this circulation that they believe is caused by the fresh water going into the North Atlantic.

So as Greenland's Ice Sheet continues to melt, it's possible that this circulation will stop altogether. Although whether or not that will definitely happen in a two-degree-warmer world is kinda the trillion-dollar question. Because, like I said earlier, that circulation also affects the ocean's surface temperature.

And that in turn will determine where rainclouds form, and where they dump their water. Meaning, in a cascade of cause-and-effect, melting ice can have significant consequences for the distribution of our planet's rainfall. Now, when we talk about rainfall, we're actually talking about two things.

One is the average rainfall an area gets in a year. The other is extremes: how often storms occur, and how intense they are. Most research says that storms will be more intense in a two-degree-warmer world, the extremes will become more extreme.

And this isn't just a hypothetical, “one model suggests that this might happen” sort of deal. It's basic physics: As water temperature increases, so does evaporation. So, storms build more easily and contain more water, and are more intense overall.

For example, India and surrounding nations can expect monsoon rains that are 25% stronger, but the droughts in-between will also last longer. The availability of drinking water is also directly linked to precipitation, and water scarcity will become a larger problem worldwide. In the end, all of these changes add up.

Even though stopping warming at two degrees would be a success, and honestly, a hard-earned victory with the way that things are going now, it would leave us with a very different world. It would be one where food is harder to come by, floods are common but drinking water is scarce, and heat waves are more frequent. And there are more consequences that we did not talk about, too, like how Arctic coastlines will change as frozen ground becomes squishy.

We're not trying to bum you out here, but it can be tough to grasp what climate scientists really mean when they say things will get at least two degrees hotter. The good news is, there are still a lot of changes we can make, both as individuals and societies, to limit the damage. So hope is not lost.

It's just a matter of putting in the work. Thanks for watching this episode of SciShow! If you wanna learn more about where organizations like the IPCC get their numbers, you can check out our episode on how climate scientists predict the future. [♪ OUTRO].