In our first lesson of this module, we're going to focus on climate change because this is the most serious issue facing all of us today. And we need to understand the magnitude of the challenge. Now again, it's likely that if you're taking this course, you already know quite a lot about climate change and the existential threat that it represents. So, the objective for this lesson is to review the basics and provide a common foundation for all of us and maybe even fill in some gaps in our own knowledge. Now, it seems to me that whenever we discuss climate change, we immediately start talking about greenhouse gasses, carbon dioxide levels and the role of fossil fuels. We're certainly going to get into those in some detail later. But for now, let's begin by answering a fundamental question, is the planet actually getting warmer? And if so, by how much, by understanding the answer to that simple question, everything else is going to make a lot more sense. Are you ready, let's get started. To answer the question is the planet warming, we need to know the temperature over a long period of time. Fortunately, people have been measuring the outside temperature ever since the creation of the thermometer. Over the last few 100 years, scientists have been measuring the temperature across the globe using weather stations such as the one that you see here in Glacier National Park. Today, organizations such as Noah, the National Oceanic and Atmospheric Administration in the United States and the Hadley Center in the United Kingdom have huge data sets of temperature measurements from around the planet. Other organizations do as well, in fact most of our knowledge about global warming and climate change comes from measurements taken by organizations like these. Let's take a look at what climate scientists do with all these data. Here is a very informative graphic published by the World Meteorological Organization or WMO for short, it is one of the most important plots will see to help us determine if the planet is actually warming. It plots the change in global temperature from the average temperature measured between 1850 and 1900. There are several important elements to this plot, so let's take a look at them one step at a time. On the X axis, you see the year from 1850 to 2020. Now, the graph looks a little jumpy representing normal variations in temperature from one year to the next. But without a whole lot of analysis, you can immediately see that temperature started to increase around 1900 and have continued to increase even up to today. But let's go even deeper, you can also see several lines superimposed upon one another. All that means is that the temperature measurements coming from several organizations such as the WMO itself, the Hadley center, Nasa, Noah, and several others. An important thing to recognize here is that the measurements from the six different scientific organizations agree with each other remarkably well. An agreement is always a good thing when you're looking at lots of data like this. Now take a look at the Y axis, the Y axis is the temperature in degrees Celsius. It refers to the change in temperature relative to the average temperature between 1850 and 1900, what the WMO refers to as pre industrial conditions. So what this graph is really showing us is how much each year's average temperature has increased since a period of relative temperature stability in this case before 1900. And all of this is measured in degrees Celsius more and degrees Celsius in a few minutes. The important result from all of this is that the answer to the question is the planet getting warmer is a resounding yes. In fact, if you look at the overall trend, you'll see that the earth's temperature has increased about 1.2°C from 1900 to today and it looks like it's still increasing. Now, if you were able to recognize that trend from the very beginning of our discussion, then well done, you clearly understand the basic idea behind one of the most important graphs in climate science. With that knowledge, let's now look at another important graph. So far, we've been talking about average global temperatures increasing about 1.2°C since 1900. Yet as this info-graphic from NASA shows the planet hasn't warmed uniformly. Some regions have gotten a lot warmer, particularly in the arctic region. Let's look at this chart in more detail, it's a projection of the world showing the change in average temperature from 2010 to 2019 relative to the average temperature between 1951 and 1978. So, it's a snapshot of how temperatures across the globe compared today versus 50 years ago. The colors represent how much the temperature has changed from that time frame. White means no change, things are pretty much the same today as they were 50 years ago. And as things get hotter, they go from yellow to orange and then to red. We can immediately see that most of the land masses have increased in temperature up to about 1.0°C. In many regions, temperatures have increased even more up to 2°C, as shown in the dark orange color. As you go more north, you can see the temperature has increased by as much as 4°C in just 50 years. If you've heard about recent heatwaves in Alaska, Greenland, or the arctic, you now see what is happening. Those regions are warming much more and much faster than anywhere else on the planet. And as we'll see throughout this course, a 4°C increase in temperature is really significant. All of the temperatures we've been talking about so far have been in degrees Celsius. This is because most of the world uses Celsius as their way of measuring temperature. For those of us in the United States, we are one of the few countries that still use the Fahrenheit temperature scale. And so, we're really not all that well calibrated when it comes to understanding what a 1° or 4°C change really means. What you see here is an illustration showing the connection between degrees Celsius and degrees Fahrenheit. At 0°C, water freezes into ice, we know that this also happens at 32 F, so, zero degrees Celsius is equivalent to 32 F. At the other end of the spectrum, water boils at one 100°C and this happens at 212° Fahrenheit. So 100°C is equivalent to 212°F. For most of us, a nice comfortable temperature at home is around 20°C, which is equivalent to exactly 68°F. Now, if you decide to increase the temperature in your home from 20 to 21°C, it will increase from 68 to 69.8° Fahrenheit. The important takeaway from this illustration is that a change of temperature of 1°C is about 1.8°F. So when climate scientists talk about an average Increase of 1.2°C, that is the same as 2.2°F. And when we hear increases of 4°C, that is the same as an increase of 7.2°F. The point here is that for some of us not calibrated in degrees Celsius, a one degree change in temperature may not sound like much, but when you convert that into degrees Fahrenheit, now that feels like something much more significant. Let's go back to our temperature graph and think about a question we often hear today. It's only 1.2°C, so how bad can it be if the average global temperature never changed again, we might be able to manage. But as our graph clearly shows the temperature is continuing to increase. In fact, it's increasing faster now than ever before, it's also getting hotter than ever before. It was recently announced by climate scientists around the world that 2020 was tied with 2016 as the hottest year ever recorded. And that comes ahead of 2019, which was the second hottest year ever recorded. And if we project out 30 or 50 years or all the way to the year 2100, what that means is temperatures will increase up to three or 4°C from the last century. And that means a lot will change on the planet, something we'll talk about in our next lesson. So what's the bottom line, that a 1.2°C change is a big change. And this will only increase if we don't do anything to slow the global rise in temperature. Let's try to put things in perspective a bit. The photo here is from Death Valley, California, the hottest place on the planet and not a place where most of us would either want to live or could live for long periods of time. In 2019, the average temperature in Death Valley was 25.1°C, or 77.2°F, not quite what you might have expected, right? That's because it gets very hot during the day and very cold during the night, so the average temperature doesn't sound all that bad. Now, the average temperature across the globe in 2019 was 13 9°C or 57 .0°F, which is pretty comfortable temperature for us. The important conclusion here is that the difference between a nice livable average temperature and one that is uninhabitable for most of us is only 11°C or about 20°F. And if we're talking about average temperature increases of up to four degrees Celsius by the end of the century, then what that means is that large parts of the planet will essentially become uninhabitable. Remember, the average temperature change doesn't tell us the whole story, some regions are warming to a much greater degree and those regions will simply be too hot to sustain life. So yes, a change of only 1.2°C is something to worry about because the trends indicate much higher temperatures if we continue to pursue a business as usual course of action. Okay, that was a lot for our first lesson, let's wrap up with a few key takeaways. Temperature records over the last 150 years are very consistent among the scientific organizations that track global temperatures. The planet has warmed about 1.2°C or 2.2°F since 1900. More importantly, global temperatures are continuing to increase and at a faster rate than ever before. In fact, 2020 and 2016 where the hottest years ever recorded, and 2019 was right behind them as the second hottest year on record. The most important point to take away is this, the planet is warming and there is no longer any doubt about that. Now that we know for sure that the earth is warming, we can think about what that really means for all of us. In our next lesson, we'll get into the consequences of a warming planet. We've already started to see some of the impacts of just a 1.2 degree change in average temperature. And in our next lesson, we'll see just what many of those impacts are. There's a lot more to come and we're just getting started, so we'll see you next time