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Video transcript

in previous videos we've already talked about the idea that there are times in Earth's orbit when it is closer to the Sun and when it is further from the Sun and when it is closer to the Sun so let's say that this is the time of the orbit when it's closer to the Sun this is the perihelion perihelion perihelion and when it is farthest from the Sun and I'm exaggerating the difference this is aphelion this is the aphelion in our orbit when we are close when we are furthest from the Sun it may be our orbit may be our orbit looks something like this so maybe our orbit looks something it shouldn't have that bulge over there so maybe our orbit looks something like this over here and what I point out in the first video where we discussed this is that this is not the cause of the seasons even though we are three percent closer right now where the way our orbit is set up and we'll see in future videos that this that the difference or the the eccentricity or how how elliptical the orbit is does change over time how much it deviates from being circular that's how you can that's one way to think about eccentricity that does change over time but right now when we are closest to the Sun we are 3% closer than when we are furthest from the Sun so 3% closer than at aphelion and we point out in the first video and rediscover tick Euler in particular perihelion when we are closest to the Sun when we actually have the most radiation from the Sun that's actually when we have the northern hemisphere when we have the Northern Hemisphere winter so this occurs right over here this occurs in January this occurs in January and aphelion occurs in July occurs in July now based on this this might lead to an interesting question because so let's think about January let's think about January when we are at perihelion and let's think about July let's think about July we're going to aphelion and let me draw a quick globe right over here and let's make that the equator and I'll draw it in both situations in both situations so January is obviously when we have the Northern Hemisphere winter so I'll call paint it in blue right over here it is winter winter and July is when we have the Northern Hemisphere summer or the southern hemisphere winter so then we have winter winter during July in the southern hemisphere and let me put summer in a in a more summery color I guess that orange is a pretty good color that's not Orange here's orange all right that's orange and that's orange so these are summer summer so that's the summer in the southern hemisphere which occurs during the winter in the Northern Hemisphere and vice versa summer in the Northern Hemisphere occurs during winter in the southern hemisphere and so the question might be rising in your head and I did see a few comments on that first video asking this question and it's a good one if we are closer if we are closer to the Sun in January or we are clearly closest to the Sun in January this is the perihelion right over here and so we're getting more solar radiation in January does that moderate the winter does that moderate the winter so does that moderate the winter in the Northern Hemisphere or I guess another way to think about it does it make the wind does it make the summer in the southern hemisphere when we are closer to the Sun does it make it more extreme does it make it more extreme or hotter and vice versa in July when we are when we are furthest from the Sun does that moderate the Northern Hemisphere winter because it's hot up there but hey we're a little bit further from the Sun and does it make the southern hemisphere winter colder so once again does it make this more extreme because it's already winter and we're further from the Sun so maybe we're also getting less radiation and so there's a couple of ways to think about it one it is true that when we're further we are getting a little bit less radiation from the Sun or we're getting heated up a little bit less but the one reality is that the southern hemisphere climate as a whole is not more extreme despite getting heated up getting more solar energy in the summer and getting less solar energy in the winter and the reason why it is not an extreme let me draw the equator here just so that we can separate our hemispheres the main reason it is believed wet it is not more extreme is that the southern hemisphere has a lot more water in it so just if you look at the surface of the southern hemisphere you're looking at a lot more water than the surface of the northern hemisphere this is of course as a Mercator projection and so it distorts things so that things near the poles get really kind of built up to look really huge even though they really aren't that big Greenland really isn't the larger than South America it just spreads them out so that you can kind of but you don't have to have so you can flatten out the map so to speak but the southern hemisphere has more water and as you may have learned in chemistry class water has a higher specific heat higher specific energy it takes a higher specific energy it takes more energy more heat to raise water a degree than it does to take to raise se to raise land of a degree and so water can absorb more energy or when there's less energy water will release more energy without dropping as much of a temperature so water has a moderating influence water has a moderating influence on the climate so I even though the summers in the southern hemisphere actually are getting more radiation than the summers in the northern hemisphere it's moderated on the actual temperature because the water has the ability to absorb more of that heat without changing the temperature as dramatically now with that said it is true that in general Antarctica is colder Antarctica is colder is colder than the North Pole but the main reason why Antarctica is colder besides the fact that it's on land as opposed to Antarctica being they are as opposed to the North Pole being in the center of the Arctic Ocean is that it's actually a huge very high altitude ice sheet and so the altitude for most of Antarctica is around 8,000 feet so it's kind of like an Alpine added altitude so the main reason why it's colder is it may be you know possibly being further away from the Sun and winter might play some role there but the main reason why it's colder is it is it's just at a much higher altitude and it's to some degree insulated from the water or I guess you could say it's on the land so especially during the long winters it's going to get that much colder but I'll leave you there and and to some degree and this is the other aspect of it during the summers the D and you know all of this stuff is super complicated so you can't you know you can't just throw it one rule of thumb and say this is the reason but these are all influences is that if you have a large super large icy sheet it's also more likely to reflect more of the energy because it's white as opposed to a darker color like the ocean or the land and so you could think about all of those factors but the general answer is it's a good question but overall the climate in the southern hemisphere is not more extreme than the climate in the southern hemisphere even though Antarctica is colder