Read Climate Change: Atmospheric Carbon Dioxide and answer the following questions. In making the calculations below, you need to be careful about 0’s. Step back from and think about your answer and check one another’s work.

1) Using the graph, “Atmospheric carbon dioxide amounts and annual emissions (1750-2021),” and other information in the paper what was the concentration of carbon dioxide the atmosphere in 1750? What was it in 2021 (according to the paper)?

2) What is the total change in concentration of carbon dioxide in the atmosphere between 2021 and 1750?

3) 1 ppm of carbon dioxide in the atmosphere is equal to about 2.13 billion tons of total carbon in the atmosphere (from https://cdiac.ess-dive.lbl.gov/pns/convert.html) or 7.82 billion tons of carbon dioxide because the carbon dioxide molecule is 3.67 times heavier than carbon. The ton used here is equal to 1000 kg.

Using the value 1 ppm of carbon dioxide = 7.82 billion tons of carbon dioxide in the atmosphere (and remember 1000 billion=1 trillion)

a) calculate how much carbon dioxide in total there was in the atmosphere in 1750

b) and how much there was in 2021.

c) How much total carbon dioxide has been added to the atmosphere between 1750 and 2021?

4) Calculate the average rate of addition of carbon dioxide to the atmosphere between 1750 and 2021. To do this, use the amount that has been added between 1750 and 2021 and divide by the number of years that passed between 1750 and 2021.

5) What was the atmospheric concentration of carbon dioxide as determined by the first direct measurements at the Mauna Loa Volcanic Observatory in 1958? Convert that concentration to tons of carbon dioxide in the atmosphere using the conversion in question 3.

6) How much carbon dioxide was added to the atmosphere between 1750 and 1958? Give your answer in tons of carbon dioxide.

7) What was the average rate of addition of carbon dioxide to the atmosphere between 1750 and 1958? Give your answer in tons of carbon dioxide per year.

8) How much carbon dioxide was added to the atmosphere between 1958 and 2021? Give your answer in tons of carbon dioxide.

9) What was the average rate of addition of carbon dioxide to the atmosphere between 1958 and 2021? Give your answer in tons of carbon dioxide per year.

10) Compare the rates of carbon dioxide addition/year that you calculated in 7 and 9. Approximately how many times bigger is the more recent figure? How do you explain such a huge change in the rate of carbon dioxide addition to the atmosphere over the 63 years between 1958 and 2021 compared to the 208 years between 1750 and 1958?

11) The active ongoing measurements of carbon dioxide in the atmosphere showed that carbon dioxide increased by 2.58 ppm during the first half of 2022 year (over a 6 month span of time). How many tons of carbon dioxide were added to the atmosphere in the first half of 2022? Convert this figure to a yearly rate of carbon dioxide increase for 2022.

12) Despite what we see from the first half of 2022, the average rate of addition of carbon dioxide to the atmosphere recently has been 35 billion tons of carbon dioxide per year–so 2022 is high. If we continue adding carbon dioxide at a rate of 35 billion tons per year, how much will we have added by 2032? Express your answer both as tons of carbon dioxide and as ppm of carbon dioxide. Compare this amount to the amount added between 1958 and 2021, during a 63 year period of time.

13) Using your figures from 12, what will the atmospheric concentration of carbon dioxide be if that much is added by 2032?

14) If that rate of addition of carbon dioxide continues without increasing until 2100, how much carbon dioxide will be added to the atmosphere from today’s amounts? Express your answer both as tons of carbon dioxide and as ppm of carbon dioxide.

15) Using your figures from 14, what would the carbon dioxide concentration of our Earth’s atmosphere be in 2100?

16) The current rate of carbon dioxide concentration appears to be unique in Earth’s recent geologic history. Measurements from trapped bubbles of air trapped in ice are shown in the paper in the graph “Carbon Dioxide Over 800,000 years.” For perspective, our species, homo sapiens, likely appeared between 550,000 – 750,000 years ago. So this graph goes back and beyond our existence as a species. What does the graph show as the range of carbon dioxide concentrations during this time?

The discussion below the graph states that 3 million years ago, carbon dioxide levels were around today’s levels of 415 ppm and that Earth’s average global temperature then was 2.5-4°C warmer and sea level was anywhere from 16-82 feet higher than it is today. Whew! That is quite a bit higher, even the lower number of 16 feet would mean nearly all of Florida would be flooded, along with lower Manhattan, and many other coastal areas around the world.

One of the things that may save us from such a fate (super high sea level and evacuating entire states and countries) is the incredibly fast rate with which we have added carbon dioxide to the atmosphere. As the paper discusses, if we were to graph the changes in carbon dioxide concentration since 1750 on a graph showing 800,000 years of time, the increase would look instantaneous. If we can add carbon dioxide at such an incredibly fast rate, then we should be able to slow down our addition or eliminate it all together. If there is no sustained human addition of carbon dioxide to the atmosphere in the future, than natural processes of removal will eventually cause carbon dioxide levels to decline. If we can succeed in this, the era of high carbon dioxide concentrations in the atmosphere might be short, causing less sustained warming and less sea level rise than would be the case if those levels were maintained for thousands and thousands of years.

The amount of carbon dioxide being “sunk” into the land and oceans is currently estimated to be 10.26 billion tons of carbon dioxide/year (from https://essd.copernicus.org/articles/14/1917/2022/essd-14-1917-2022.pdf). So that is the amount that is estimated to be removed from the atmosphere on a yearly basis by natural processes. That number changes depending on several factors, but if we just use it as a way to do a crude estimation, then we can guess how long it might take to remove the carbon dioxide we have added to the atmosphere since 1750, if we want to dial conditions back to that time period.

17) Using that number at face value, how long would it take to remove the carbon dioxide that has been added to the atmosphere since 1750 (use your figure from question 3)?

18) Carbon dioxide is being added to the atmosphere by natural processes also. If you accounted for the rate of natural addition of carbon dioxide to the atmosphere, how would that change the amount of time estimated to get back to the carbon dioxide levels of the year 1750?

19) Look at the graph “Past and future atmospheric carbon dioxide” in the paper. The graph shows different scenarios for the future using different rates of addition of carbon dioxide. The estimates we made in question 17 are crude and do not account for the complex, real world behaviour of carbon dioxide. The graph uses a model that does take this complex behaviour into account. In the most optimistic scenario, by about what year does the world need to bring net emissions of carbon dioxide to 0? What is the resulting predicted carbon dioxide concentration in the atmosphere in 2100 in that scenario?

20) Using the graph in question 19, what is the predicted carbon dioxide concentration in 2100 if we follow a path where we maintain our current levels of carbon dioxide emission until 2050 and then decrease it after that?

21) Let’s make these huge numbers personal. The average driver in an average gasoline powered car emits 4.6 tons of carbon dioxide per year (according to the United States government agency EPA). Given that the average rate of carbon dioxide addition to the globe by people’s activities is 35 billion tons of carbon dioxide per year, how much would that global rate of addition change if every one of the 280 million vehicles (cars and trucks, so our 4.6 tons of carbon dioxide/year is an underestimate) in the United States were converted to electric vehicles powered through renewable energies such as solar? What if every ground vehicle on the planet were converted to electric, that is 1.446 billion vehicles?

22) Given what you learned about energy in last week’s discussion and your figures from 21, what energy sector that uses fossil fuels (electricity/power generation or transportation) needs to be converted to a non-fossil fuel type to have a big affect on carbon dioxide emissions?