Geology multiple choice

Daniel Kevins

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Q1. What causes substantial changes in carbon dioxide concentrations over the course of a single day?

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Q2. What causes substantial changes in carbon dioxide concentrations over timescales of months?

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Q3. What causes substantial long-term changes in carbon dioxide concentrations (changes over the course of years and decades)?

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Let’s have a look at how carbon dioxide has varied over the past decades. Below is a graph made from individual measurements of the atmosphere taken regularly throughout the year. The measurements are of carbon dioxide (CO2) in the atmosphere, measured in parts per million, or “ppm” (how many out of 1 million molecules in the atmosphere are carbon dioxide molecules).

Remember Mauna Loa in Hawaii? This shield volcano, sticking way up into the atmosphere, way out in the middle of the Pacific away from big cities and such, is one of the fairly ideal places where such measurements are taken. Note that CO2 levels wiggle up and down with a set frequency: these are the seasonal cycles from Q2. Note also the long-term trend, averaging out these little wiggles. Look at this long-term trend for the following questions.

co2-1.png

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Q4. What was the approximate level of carbon dioxide in the atmosphere measured in 1960 (60 years ago)?

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Q5. What is the approximate level of carbon dioxide in the atmosphere this year (2020)?

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Q6. This represents an increase of about how much?

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Q7. Dividing the current value by the earlier value, then multiplying by 100%, indicates proportionally how much higher the current levels are. Take your answer to Q5, divide by your answer to Q4, and multiply by 100%. The current level of carbon dioxide in the atmosphere is about:

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Now, let’s look at temperature measurements. These are easier to make than measurements of carbon dioxide concentration, and so our record of these goes back farther. NASA shows the global temperatures as how much below (negative numbers) or above (positive numbers) an average value they are:

https://climate.nasa.gov/vital-signs/global-temperature/ (Links to an external site.)

These measurements are in degrees Celsius, rather than degrees Fahrenheit.

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Q8. From 1880 to 1926, the curve is fairly flat, indicating that global temperature did not change substantially. If this trend were extrapolated to the present day, what global average temperature anomaly would be predicted?

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Q9. What did the temperature do between 1940 and 1964?

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Q10. From 1964 to the present, temperature has increased steadily overall, though with lots of up-and-down fluctuations. About what was the global temperature anomaly last year (in 2019)?

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Q11. How much higher is the value in Q10 from the value in Q8?

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Q12. How much of a temperature difference is this in Fahrenheit?

To convert, take the value in Celsius, then multiply by 1.8.

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This is how much the global temperature has risen in the past century (and mostly in the past 60 years).

The primary cause of this increase has been the increase in carbon dioxide in the atmosphere, as shown in your previous plot. However, if carbon dioxide was the only factor influencing temperature, then there wouldn’t be these wiggles in the temperature plot. Whereas carbon dioxide is the single most important factor, various other things can impact the climate. Two of them are volcanic eruptions and the El Niño–Southern Oscillation (ENSO): https://en.wikipedia.org/wiki/El_Ni%C3%B1o%E2%80%93Southern_Oscillation (Links to an external site.)

Let’s look at each of these in turn. First, volcanic eruptions. Here are some major eruptions from the past century, and the years that they occurred:

1883 Krakatau

1902 Santa Maria

1968 Fernandina Island

1991 Pinatubo

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Q13. Hover your cursor over the data points on the plot, and it will display the year and the temperature anomaly for that data point. Find the years of the volcanic eruptions listed above, and examine the temperature anomaly that year, and the year after the eruption.

In general, in the year after the eruption, the temperature:

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Q14. Volcanoes release heat and greenhouse gases (remember all those trapped gases in the lava?), which contribute to warming, but also lots of material into the atmosphere, which partially blocks sunlight and contributes to cooling. Based on your answer to Q14, which effect is more important in the year following the eruption?

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Second, the El Niño–Southern Oscillation (ENSO). Below are El Niño years of this oscillation, or cycle, from the past seventy years:

1951, 1953, 1957, 1963, 1965, 1969, 1973, 1977, 1983, 1987, 1991, 1997-1998. (For El Niño events starting near Christmas time, the following year is listed, since that is when the peak temperature anomaly usually occurs.)

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Q15. Wave your cursor over the data points again, finding these years and looking at the temperature anomaly during these El Niño years and comparing them to the temperature anomaly the year before. In general, going from the year before an El Niño year to an El Niño year, the global temperature:

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You may have noticed that some of the El Niño years don’t have the typical pattern as the rest. Most of these are years when volcanic eruptions also occurred, and the two effects are stacking!

Hopefully, this illustrates some of the complexity in climate patterns through time. There is also complexity by location. Please watch this video illustrating this: warmer than average temperatures for a given region are shown in warmer colors, and colder than average temperatures for that region are shown in cooler colors. Note both the overall warming trend, and also that this pattern is not uniform across the Earth. https://svs.gsfc.nasa.gov/4787 (Links to an external site.)

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Last year was the second warmest year on record (for now; the warmest was 2016). Let’s look at one of these temperature anomaly maps specifically for last year. Go to: https://data.giss.nasa.gov/gistemp/maps/ (Links to an external site.)

Then, change “Mean Period” to “Annual (Jan-Dec)”, so that we are considering the entire year. Set the “Time Interval” to “Begin” 2019 and “End” 2019. Leave the other settings in their defaults, and click “Make Map.”

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Q16. In 2019, what part of the Earth experienced the most anomalously warm temperatures?

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Q17. What inhabited area experienced anomalously cold temperatures?

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Q18. What part of the Earth experienced the most anomalously cold temperatures?

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