Sea levels in the Pacific

I recently visited Port Vila, capital of the Pacific island nation of Vanuatu (the photo above is from the Port Vila waterfront). Port Vila is the site of a sea-level measuring station. It is interesting that, although local newspapers are deeply concerned about sea level rise, the average sea level rise between 1993 and 2017 at Port Vila was essentially zero (see chart below, which uses LOESS smoothing of monthly measurements).

How can this be? Aren’t global sea levels rising at 2–3 mm per year? Well, “global sea level” is a rather theoretical concept. Ocean temperatures are not uniform. Some islands are rising out of the ocean. Others are sinking. Air pressure, and the El Niño Southern Oscillation cycle, have a huge effect on sea levels too. As they say, it’s complicated.

The NASA map below shows that some areas of the Pacific have actually seen a long-term reduction in sea level (independent of any upward or downward movement of land). Other areas, of course, have seen quite rapid increases (the increases and decreases average out to a rise of about 3 mm per year). The map covers data only up to 2008, however. Since 2008 was roughly the peak for the Port Vila data, it doesn’t quite explain the last decade of the graph above. If I had to guess, I’d assume that some of those sea-level-decrease areas on the map had shifted a bit.


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Support for Kavanaugh vs support for Trump

Brett Kavanaugh has been in the news rather a lot lately. The chart above shows support for his appointment to the US Supreme Court, for various demographic groups, as per a 1 October Quinnipiac University Poll. This is compared to the 2016 Trump vote for those same groups, as per CNN exit polls (in both cases, some missing information had to be inferred using the data provided plus census data). The area of the circles shows the size of the various groups.

Responses to Kavanaugh seemed largely to follow partisan lines. Democrats mostly went one way, Republicans the other. However, white women seemed to support Kavanaugh less than expected, perhaps because they were more likely to believe the accusations made against him. Minority groups, on the other hand, were more supportive of Kavanaugh than of Trump, perhaps because of concerns about evidence, corroboration, and due process. Overall, it seems to almost balance out, though – I must say that I can’t see any support here for a “blue wave” at the November elections.


Would y’all like to see a map?

The word y’all is used as a second person plural pronoun in the United States (although in my travels I have also heard it used as a polite singular). The map above (click to zoom) shows the average frequency of use by state, according to the 2003 Harvard Dialect Survey. The usage is primarily Southern.

English needs a second person plural pronoun, it seems to me. What do all-y’all think?

Image produced using the maps package of R. Other visualisations of the survey exist.


2019 Bridgestone World Solar Challenge: preliminary list


Western Sydney at the 2017 Bridgestone World Solar Challenge (photo: Anthony Dekker)

The 48 teams listed below (26 Challengers, 21 Cruisers, and 1 Adventure car) have expressed interest in the 2019 Bridgestone World Solar Challenge next October (social media links have not all been checked – some might no longer work):

This page last updated 21:30 on 18 October 2018 AEDT


In praise of duct tape

It’s a common joke that engineers fix everything with duct tape. I’m happy to say that there’s no truth in that whatsoever.*

Photos: Punch Powertrain Solar Team (iLumen European Solar Challenge 2018), Tshwane University of Technology (Sasol Solar Challenge 2018), Solar Energy Racers (Sasol Solar Challenge 2018), Western Sydney University (World Solar Challenge 2015).

*: not everything.


New Horizons status check

The New Horizons spaceprobe, having given us some lovely pictures of Pluto in 2015, is on its way to the Kuiper belt. But what is the Kuiper belt? Named after Dutch-American astronomer Gerard Kuiper, the Kuiper belt is much like the asteroid belt, but much larger, about 15 times further out from the Sun, and far less well understood.

Initially, New Horizons is headed for the rock, or perhaps pair of rocks, (486958) 2014 MU69, which NASA has nicknamed Ultima Thule. The space probe is due to reach it on January 1st (which will be just short of 13 years after its launch). Currently, New Horizons is 6,360,000,000 km or 5.9 light-hours from Earth, and has recently completed a course-correction manoeuvre.


A Day in the Life of Solar Energy Racers

By special request, here is another day in the life post, this time for Swiss solar car team Solar Energy Racers (SER). The day is 29 September, the last day of the Sasol Solar Challenge. I am relying on information from a blog by SER strategy person Georg Russ, together with GPS data screen-scraped off the race tracker by a friend, and elevation data from the Shuttle Radar Topography Mission. As before, the horizontal axis of the chart represents distance.

The day began at Swellendam, and the team drove to the control stop at Bredasdorp, stopping there for 30 minutes the first time (it can be seen from the chart that SER was not quite so good as Nuon at maintaining a consistent speed). The team drove two loops, the first of them to Cape Agulhas (the southernmost point of the African continent, and the site of a picturesque lighthouse). It can be seen from the chart that they had to stop on the way (to repair a loose left rear wheel fairing – with duct tape, of course).

The team completed one more, shorter, loop, before heading on to the finish at Stellenbosch (Nuon drove that shorter loop three times). Knowing when to quit driving loops was an important strategy decision. The chart highlights the hilly nature of that final leg (going through part of the Cape Fold Belt), as well as some stops to change drivers.

Georg Russ notes an energy output for the day of 5.35 kWh (with 0.64 kWh recovered), and a photovoltaic input of 4.63 kWh, giving a net battery drain of 0.08 kWh. Pretty good!