GlobalTempLab-2

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Dec 6, 2023

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Laboratory Exercise #1: Global Average Temperatures I. Introduction Since the mid-19th century, weather stations have recorded temperatures at various locations on land and water around the world. From about 1880 onwards, the number and distribution of stations have been large enough to provide an adequate sample of global surface temperature variations from year to year. This temperature record provides central evidence of recent global climate change and demonstrates humankind's potential to modify Earth's climate. Satellites, with extensive global coverage, have been recording even more accurate estimates of global temperature (in the lower troposphere, not at the Earth's surface) since the 1980s. Do note that satellite data are not included here. In this lab, your team will analyze the global surface temperature record from 1880 to the present. You will evaluate long-term trends and shorter-term fluctuations, and you will look for evidence of climate forcings and mechanisms of natural variability on the global surface temperature. The goal is to give you a sense of the complexity encountered when extrapolating recent temperature trends into the future, and the need for models to make reasoned predictions of temperature change. II. Instructions Type up brief answers to the questions asked in Tasks 1 through 3. Include graphs, tables, and calculations as needed, and explain the reasoning behind your answers. A. Fluctuations of the global climate Open the Global Average Temperature file in Excel. The data are saved in columns, with the year in column A, and global mean annual temperature in column B. Task 1 (25 points) : Choose 10 non-successive years at random, and compare the average annual temperature in each year to that of the following year (e.g., if 1871 and 1925 are two of your ten years, compare 1871 to 1872, 1925 to 1926, and so on). Example Year set Average Temp (C) Yearly change 1883 13.76 1884 13.7 -0.06 1
Laboratory Exercise #1: Global Average Temperatures Year set Average Temp (C) Yearly change What is the typical magnitude (i.e., ignoring the sign) of the year-to-year global average temperature changes? Of your 10 years, how many times did the temperature increase/decrease in the following year? Increase: ________ times Decrease: ________ times Does it seem possible to predict whether next year is going to be warmer than this year globally? 2
Laboratory Exercise #1: Global Average Temperatures B. Decadal-to-century variability and trends Task 2 (25 points) : Make a chart of annual temperature vs. time for the years 1880-2022 and calculate its slope using a trendline. (Paste the chart here.) How would you describe the general appearance of the 1880-2022 curve? Describe the major features of the global temperature time series. How much warming has occurred over the entire time series? What are the 5 warmest years in the record? The 5 coldest? Have we come anywhere close to having one of the coldest years in the record during your team’s lifetime? Now make a chart of annual temperature vs. time for only the years 1975-2022 . (Paste the chart here.) How does the 1975-2022 slope compare to the 1880-2022 slope, and what does this indicate? 3
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Laboratory Exercise #1: Global Average Temperatures As you have seen in class, carbon dioxide has been increasing in concentration over the 20 th century. Discuss how this is related to the temperature time series you are examining. Is CO 2 a perfect global temperature predictor? Why or why not? How long a record do you think is needed to see clear evidence of global warming? Explain. C. Interannual Variability (Choose one of the following tasks.) Choice 1 - Task 3 (50 points) : Following is a list of major volcanic eruptions since 1880 and the year that each occurred: 1883 Krakatau 1890 Unidentified 1902 Soufriere/Pelee 1902 Santa Maria 1964 Agung 1982 El Chichon 1991 Pinatubo 2006 Tungurahua For any four of the above eruptions, note the average annual global temperature for the year in which the eruption occurred, the year before the eruption, and list temperatures for three to five years after the eruption. Eruption 1 (Year: ) Eruption 2 (Year: ) Temperature (°C) Temperature (°C) Eruption year Year prior 3-5 yrs after Eruption year Year prior 3-5 yrs after Yr 1 Yr 2 Yr 3 Yr 4 Yr 5 Yr 1 Yr 2 Yr 3 Yr 4 Yr 5 Eruption 3 (Year: ) Eruption 4 (Year: ) Temperature (°C) Temperature (°C) Eruption year Year prior 3-5 yrs after Eruption year Year prior 3-5 yrs after 4
Laboratory Exercise #1: Global Average Temperatures Yr 1 Yr 2 Yr 3 Yr 4 Yr 5 Yr 1 Yr 2 Yr 3 Yr 4 Yr 5 What is the typical magnitude and sign (warming or cooling) of the effect that large volcanic eruptions have on global climate? How long does it take for the climate to return to “normal” after a major eruption? Comparing what you know about global temperature trends and the overall impact of aerosols (both natural and anthropogenic) on current climate, do you think it would be wise to invest in stratospheric aerosol injection to attempt to modulate atmospheric temperatures over the near to mid-term? Weigh some basic pros and cons of this approach, and look back on the slides in the Earth’s Energy Balance & Radiative Forcing discussion if necessary. 5
Laboratory Exercise #1: Global Average Temperatures 1991 Pinatubo eruption https://pubs.usgs.gov/fs/1997/fs113-97/ Choice 2 - Task 3 (50 points) : El Niño and La Niña are the warm and cool phases, respectively, of a recurring climate pattern across the tropical Pacific: the El Niño-Southern Oscillation, or ENSO. Below is a graphical representation of ENSO years in recent times. As you can see, the pattern can shift back and forth irregularly every two to seven years, and each phase triggers predictable disruptions of temperature, precipitation, and winds. These changes disrupt the large-scale air movements in the tropics, triggering a cascade of global side effects. Oceanic Niño Index (ONI) Selecting the strongest El Niño (red) and La Niña (blue) events (marked by month/year) will give you the best chance of identifying a temperature signal in the dataset. Before making the final selection of the ENSO years your team will analyze, look at both of the following datasets: 6
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Laboratory Exercise #1: Global Average Temperatures NOAA’s National Weather Service Climate Prediction Center for three-month running averages of above (red) and below (blue) normal sea surface temperatures (SSTs). Temperature anomalies beyond the +/-0.5˚C threshold for the Oceanic Niño Index (and for a minimum of 5 consecutive overlapping seasons) are shown in color. Larger temperature anomalies indicate stronger events. NOAA’s Physical Sciences Laboratory for the top 24 ranked strongest El Niño and La Niña event years by season. These tables show similar data as the above link, but rank the strongest ENSO years by season rather than showing the magnitude of seasonal temperature anomalies year by year. Choose two El Niño events and two La Niña events (but not ones that occurred during the year of a major volcanic eruption; see above). Note the average annual global temperature for the ENSO year, for two years before the event, and for two years after the event. El Niño event 1 El Niño event 2 Temperature (°C) Temperature (°C) Two years prior One year prior ENSO year One year after Two years after Two years prior One year prior ENSO year One year after Two years after La Niña event 1 La Niña event 2 Temperature (°C) Temperature (°C) Two years prior One year prior ENSO year One year after Two years after Two years prior One year prior ENSO year One year after Two years after Can ENSO be detected in the global temperature even though it is basically a tropical phenomenon? 7
Laboratory Exercise #1: Global Average Temperatures By how much and in which direction (warming or cooling)? Discuss your data for El Ni ñ o and La Ni ñ a events separately. How do you think ENSO may respond to continued climate change (atmospheric and oceanic warming) and what may be the resultant associated climate impacts? Upload the lab assignment as a doc, docx, xls, xlsx, or pdf via UNM Canvas by the end of class. I am unable to open pages or numbers files . 8 2015 2016 2019 2015