How will the warming impact humanity and other living species?

It is one thing to document a rise in average global temperatures. It is another thing to assess what the impacts of that increase in temperature means for humans and other species.

You may be saying, “But a 1.5 degrees Celsius average global temperature increase doesn’t seem like a big deal. If it gets 1.5° C (2.7° F) hotter or cooler outside on any given day, it’s not the end of the world.” You’re right, it doesn’t seem like a big deal, but it is. Plus, the warming is not over or stabilizing. It is still increasing.

Seemingly small average global temperature changes make a big difference. When it was 2° C cooler (on average), Chicago was covered in glacial ice…all year! Has the Earth been much hotter? Yes, the poles have fossil evidence of tropical animals and vegetation, but it has never been much hotter than it is now when humans lived on the planet. As long as civilization as we know it (domesticated animals, agriculture, permanent human settlements, etc.) has been around (+/- 10,000 years), the temperature has been +/- 1° C of what it is today. So, it is the degree of change (how much change) that scientists are concerned about. Scientists are also concerned about the rate of change (how fast it will change). Homo sapiens have lived through a couple of ice ages but those changes occurred slowly and allowed adaptation or change for better chances of survival. Also, during past changes to the climate, the Earth was not as densely populated with humans as it is now. In 1804 the population of the planet was estimated to be 1 billion people, by 2000 there were 6 billion and we are now over 7 billion. The planet is on a trajectory to become too hot too fast for the well-being of humans and other species.

Additionally, 1.5° or 2.0° C average global temperature rise means that some regions would see higher than 1.5° or 2.0° rise and other regions lower. Tropical nations, many of them with higher rates of poverty (for example, many African nations), would see a higher average temperature increase than the U.S. and European countries. That’s because most nations in the tropics already have higher average daily temperatures and less temperature variation throughout the year. Higher rates of poverty mean they are more vulnerable to such changes (more on that later). Find some of this research here. In 2018, scientists predicted we will reach 1.5° C above preindustrial levels by between 2030 and 2050.

So, what are the consequences of the planet warming? It depends on how much it warms. It literally is a matter of degree. I will try to explain some of the consequences that are occurring and what scientists predict could occur, but remember, it depends on how much the planet warms which largely depends on what policies nations, states, and cities successfully implement, and what actions societies take collectively at the global level to curb the warming trend.

Remember the figure below from the previous section? Future warming is driven by and dependent on human actions.

The solid black line represents the actual Gigatons of CO2 equivalent emissions emitted globally. The gray band then represents the “business as usual” trajectory (with more error or uncertainty as the projections get further into the future). This would lead to 4.1-48° C warming by 2100. The darker blue band represents emissions reductions and subsequent temperature estimates if current policies are implemented and effective. This would lead to a 2.8-3.2° C rise. The light blue band is based on commitments nations have made under the Paris Accord. The yellow and light green bands show how dramatically we would need to reduce emission to limit the increase in temperature to 1.5 and 2.0 degrees respectively.

HEAT The first consequence is that it will get hotter. That seems like a no brainer but heat waves kill. Back in 1995 a heat wave in Chicago killed over 700 people. A 2003 heat wave across Europe killed 70,000 people! A 2019 heat wave in India raised temperatures to 123° F and a 2016 heat wave in the Middle East caused temperatures in cities in Kuwait and Iraq to reach 129° F. But won’t warming decrease the number of cold related deaths? Yes, there will be some “benefits” of climate change, but on the whole, the negative and damaging consequences (more below) will outweigh the few positive impacts.

What will the city you live in feel like in 2100? Click the image below for a tool that shows what some cities in the continental US will feel like by 2100.

Another tool shows the number of days above a certain temperature (95° – 115° F) each city is predicted to experience compared to current temperatures. For example, below are the projections for Chicago which currently experiences less than a handful of days above 95° a year. By 2050, it is projected that nearly two months of the Chicago summer will be above 95° F.

In Phoenix, Arizona there are currently very few days above 115° F but by 2050, science predicts 20 days a year above 115° and at current emissions trends, two full months above 115° by 2100!

The science behind such figures can be found here.

In a 2020 article, an interdisciplinary group of scholars concluded that “for thousands of years, humans have concentrated in a surprisingly narrow subset of Earth’s available climates, characterized by mean annual temperatures around ∼13 °C (55° F) [remember this is a global average through all seasons of the year]. This distribution likely reflects a human temperature niche related to fundamental constraints. We demonstrate that depending on scenarios of population growth and warming, over the coming 50 years, 1 to 3 billion people are projected to be left outside the climate conditions that have served humanity well over the past 6,000 years.

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