How does climate change impact the spin axis of the planet?

Source: NASA

NASA’s Vital Signs of the planet post, Scientists ID three causes of Earth’s spin axis drift (9/19/18) explains changes in the spin axis.

Earth is not a perfect sphere. When it rotates on its spin axis — an imaginary line that passes through the North and South Poles — it drifts and wobbles. These spin-axis movements are scientifically referred to as “polar motion.” Measurements for the 20th century show that the spin axis drifted about 4 inches (10 centimeters) per year. Over the course of a century, that becomes more than 11 yards (10 meters).

In general, the redistribution of mass on and within Earth — like changes to land, ice sheets, oceans and mantle flow — affects the planet’s rotation. As temperatures increased throughout the 20th century, Greenland’s ice mass decreased. In fact, a total of about 7,500 gigatons — the weight of more than 20 million Empire State Buildings — of Greenland’s ice melted into the ocean during this time period. This makes Greenland one of the top contributors of mass being transferred to the oceans, causing sea level to rise and, consequently, a drift in Earth’s spin axis.

The article explains why the Greenland Ice sheet has such an impact. NASA has also produced an interactive simulation on how different processes contribute to the wobble. There could be a nice vector calculus, linear algebra, or geometry exercises here.

How have wages grown since 1980?

Source: EPI

Wage growth has varied depending on numerous factors such as gender, race, income level, and education. The EPI article,  America’s slow-motion wage crisis-Four decades of slow and unequal growth by John Schmitt, Elise Gould, and Josh Bivens (9/13/18) summarizes the findings with 30 graphs or tables (data included). For example, the cumulative percent change in inflation-adjusted hourly wages for workers in the 10th, 50th, and 90th percentile is given in the graph here (downloaded from the article).

The first key trend since 1979 is the historically slow growth in real wages. In 2017, middle-wage workers earned just 16.8 percent more than their counterparts almost four decades earlier. This corresponds to an annualized inflation-adjusted growth rate over the 38-year period of just 0.4 percent per year. The real wage increase for low-wage workers (those at the 10th percentile) was even slower: 8.9 percent over 38 years, or a 0.2 percent annualized growth rate.

This slow growth is particularly disappointing for two reasons. First, as we will see in the next section, U.S. workers today are generally older (and hence potentially more experienced) and substantially better educated than workers were at the end of the 1970s.10 Second, for workers at the bottom and the middle, most of the increase in real wages over the entire period took place in the short window between 1996 and the early 2000s. For the large majority of workers over the last four decades, wages were essentially flat or falling apart from a few short bursts of growth.

Quiz Questions: What was the cumulative change in hourly wages from 1979 to 2017 for

  1. What was the cumulative change in hourly wages from 1979 to 2017 for workers with an advanced degree?
  2. What was the cumulative change in hourly wages from 1979 to 2017 for workers with less than a high school diploma?
  3. Which ethnic group had the greatest change?
  4. What was the cumulative change in hourly wages from 1979 to 2017 for Women in the 50th percentile?
  5. What was the cumulative change in hourly wages from 1979 to 2017 for Men in the 50th percentile?

The article and/or corresponding data is ready for use in a stats or QL course in the 90th percentile.

Answers: (1) 30.0% (2) -9.6% (3) Asian American/Pacific Islander non-Hispanic 23.3% (4) 33.8% (5) 8.1%.

How much do countries spend on education?

The answer to the question depends on how it is measured.  The post  in statista, The Countries Spending the Most on Education by Martin Armstrong (9/12/2018) reports spending as a share of gross domestic product for primary, second and post-secondary non-tertiary education as well as tertiary education.  By this measure Norway spends the most. But, if the measure used is expenditure per student as a share of GDP per capita, the high spender is (south) Korea (Norway is fifth). Our graph here is a scatter plot of the two measures by country.

The data is from OECD.Stat. Go to Education and Training, Education at a Glance, Financial resources invested in education, Education finance indicators, and finally Expenditure per student as share of GDP per capita.  Under indicator at the top of the spreadsheet the measure can be changed.  Definitions of measures can be found in the OECD Handbook for Internationally Comparative Education Statistics (page 99).

Download the csv file and R-script used here.

How are blocking high, climate change, & hurricane Florence related?

Credit: via Think Progress

The Think Progress article, Global warming ‘double whammy’ may be steering Florence into the Carolinas, says researcher by Joe Romm (9/12/2018) makes the connection.

The path of Florence has been extremely unusual. As Philip Klotzbach, an Atlantic hurricane expert, tweeted on Friday, “33 named storms (since 1851) have been within 100 miles of Florence’s current position. None of these storms made US landfall. The closest approach was Hurricane George (1950) — the highlighted track [in white].”

Florence, tragically, has made a beeline toward the Carolinas. And it clearly was steered away from the historical (or “climatological”) path by a major high-pressure system blocking its typical path — north and away from land.

Back in 2016 Francis published a study on the link between blocking highs and global warming. At the time, she told ThinkProgress: “Our new study does indeed add to the growing pile of evidence that amplified Arctic warming and sea-ice loss favor the formation of blocking high pressure features in the North Atlantic. These blocks can cause all sorts of trouble…”

There are more details in the well cited article. Sustainabilitymath posted about hurricanes last year, Are We Seeing More Hurricanes in the North Atlantic?, which inlcudes a link to hurricane data.

What do we know about plastics?

The Our World in Data article Plastic Pollution by Hannah Ritchie and Max Roser (Sept 2018) is a detailed summary of plastics with 20 charts.  For example, one of the charts is a time series of plastic production (downloaded and posted here) showing that, in 2015, the world produced 381 million tons of plastic. In the same year, only 20% of the plastic was recycled (second chart in the article).  There is information on plastic waste generation.

Packaging, for example, has a very short ‘in-use’ lifetime (typically around 6 months or less). This is in contrast to building and construction, where plastic use has a mean lifetime of 35 years.7 Packaging is therefore the dominant generator of plastic waste, responsible for almost half of the global total.

Who produces the most plastic waste?

… we see the per capita rate of plastic waste generation, measured in kilograms per person per day. Here we see differences of around an order of magnitude: daily per capita plastic waste across the highest countries – Kuwait, Guyana, Germany, Netherlands, Ireland, the United States – is more than ten times higher than across many countries such as India, Tanzania, Mozambique and Bangladesh.

As always with Our World in Data, the data associated with each graph is downloadable.

How many 90+ degree days will your hometown have in the future?

The New York Times interactive article How Much Hotter Is Your Hometown Than When You Were Born? By Nadja Popovich, Blacki Migliozzi, Rumsey Taylor, Josh Williams and Derek Watkins, allows the reader to input a birth year and hometown and provides a graph with historical 90+ degree days and predictions for the future. For example a person born in 1970 in NYC would get the graph copied here.  In 1970 the expectation was six 90+ degree days, today it is 11, and by 2050 it will be 24 with a likely range of 15 to 30.

THE NEW YORK AREA is likely to feel this extra heat even if countries take action to lower their emissions by the end of the century, according to an analysis conducted for The New York Times by the Climate Impact Lab, a group of climate scientists, economists and data analysts from the Rhodium Group, the University of Chicago, Rutgers University and the University of California, Berkeley. If countries continue emitting at historically high rates, the future could look even hotter.

The future projection shown here assumes countries will curb greenhouse gas emissions roughly in line with the world’s original Paris Agreement pledges (although most countries do not appear on track to meet those pledges).

There are related human health impacts:

Worldwide, high temperatures have been found to increase the risk of illness and death, especially among older people, infants and people with chronic medical conditions. Lower-income populations, which more often lack access to air conditioning and other adaptive technologies, are also more likely to suffer the impacts of extreme heat. In America, so are people of color.

The article has other graphs and quantitative information which can be used in  QL based course.

How distracting are cell phones?

The extensive article by Pew Research, How Teens and Parents Navigate Screen Time and Device Distractions by Jingjing Jiang (8/22/18), presents detailed data on cell phone use.  For example,

And 51% of teens say they often or sometimes find their parent or caregiver to be distracted by their own cellphone when they are trying to have a conversation with them.

As they look at their own lives and those of their peers, most teens see things that worry them. Roughly nine-in-ten teens view spending too much time online as a problem facing people their age, including 60% who say it is a major problem.

The article has eight charts, one of which is reposted here.  There is a complete methodology section, which is perfect for a stats class, with enough information to use the data for statistical tests.

How has Arctic sea ice volume changed?

The Guardian article Arctic’s strongest sea ice breaks up for first time on record by Jonathan Watts (8/21/18) includes an animated graph of Arctic sea ice volume by year. We produce a similar graph using monthly average ice volume from PIOMAS (source cited for the data in the article).  The graph clearly displays the change of ice throughout the year and the loss of ice throughout the years.

Freakish Arctic temperatures have alarmed climate scientists since the beginning of the year. During the sunless winter, a heatwave raised concerns that the polar vortex may be eroding.

This includes the Gulf Stream, which is at its weakest level in 1,600 years due to melting Greenland ice and ocean warming. With lower circulation of water and air, weather systems tend to linger longer.

A dormant hot front has been blamed for record temperatures in Lapland and forest fires in Siberia, much of Scandinavia and elsewhere in the Arctic circle.

The data from PIOMA includes monthly and daily ice volumes.  The R script and csv file that produced the graph here can be downloaded.

What is the pay gap between black women and white men?

EPI has the answer in the post Separate is still unequalHow patterns of occupational segregation impact pay for black women by Madison Matthews and Valerie Wilson (8/6/2018).

On average, in 2017, black women workers were paid only 66 cents on the dollar relative to non-Hispanic white men, even after controlling for education, years of experience, and geographic location. A previous blog post dispels many of the myths behind why this pay gap exists, including the idea that the gap would be closed by black women getting more education or choosing higher paying jobs. In fact, black women earn less than white men at every level of education and even when they work in the same occupation. But even if changing jobs were an effective way to close the pay gap black women face—and it isn’t—more than half would need to change jobs in order to achieve occupational equity.

Along with the graph copied here, there is a time series from 2000 to 2016 of the Duncan Segregation Index:

the “Duncan Segregation Index” (DSI) for black women and white men, overall and by education, based on individual occupation data from the American Community Survey (ACS). This is a common measure of occupational segregation, which, in this case identifies what percentage of working black women (or white men) would need to change jobs in order for black women and white men to be fully integrated across occupations.

Data is available for both graphs.

What percent of doctors are female?

OECD has the answer in their post Women make up most of the health sector workers but they are under-represented in high-skilled jobs (3/2017) along with a nice graphic.

The current overall health workforce is mostly composed of women. Nonetheless, female health workers remain underrepresented in highly skilled occupations, such as in surgery. As of 2015, just under half of all doctors are women across OECD countries on average. The variation across countries is significant: in Japan and Korea only around 20% of doctors are women, in Latvia and Estonia this proportion is over 70%.

It is worth noting that the U.S. is well below the OECD average with only 34.1% of its doctors female in 2015, although the current posted data set has the U.S. at 35.06% for 2015 (35.52% for 2016).

Time series data for OECD countries is available at the OECD.stat Health Care Resources page. Data for the U.S. dates back to 1993 (19.59%) through 2016.  For this specific data set click physicians by age and gender on the left side bar.  Within the chart click variable, measure, and year, to change the scope of the data in the spreadsheet. The data can be downloaded in multiple formats.