Secretary of State John Kerry disembarks from his U.S. Air Force aircraft at the Pegasus ice runway near McMurdo Station, Antarctica on Friday, Nov. 11, 2016. (AP Photo/Mark Ralston, Pool)

(Update: A reader points out that the calculations in this story are based on a first-class passenger flying commercial, whereas it would be more fitting to calculate CO2 emissions for the entire aircraft in the case of Secretary of State John Kerry’s dedicated Boeing 757. One source puts average CO2 emission for aircraft at 53.3 pounds per air mile, so Kerry’s current trip could be said to be responsible for 853.4 metric tons of CO2 – as many as 52 average Americans produce in a year.)

(CNSNews.com) – Secretary of State John Kerry winged his way Monday from New Zealand to the Middle East on the next leg of what may be his longest trip yet, a journey during which America’s top diplomat will account for roughly 16.5 tons of carbon dioxide emissions.

That’s more or less the amount of CO2 – one of the key “greenhouse gases” blamed for global warming – produced by the average American in a full year, according to World Bank data.

Climate change features prominently on Kerry’s itinerary on his current trip, an eight-day haul from Washington to New Zealand to Antarctica – where he became the highest-ranking U.S. official to visit – and on to two Arab Gulf states and then Morocco before winging to Peru and then back home.

The Antarctica visit, which included a stop at the McMurdo research station on Ross Island, was focused primarily on climate change – Kerry spoke about concerns that should a huge ice sheet break up and melt sea levels could rise by 12 feet.

The trip to Morocco is also climate-focused: Kerry will attend the U.N. climate conference in Marrakesh, where is expected to deliver a speech to an audience deeply concerned about President-elect Donald Trump’s views on climate change and the new Paris climate accord.

An imprecise calculation of the route Kerry is taking on this trip indicates he will travel around 35,300 miles, which would make it the longest of Kerry’s many journeys as secretary of state.

Secretary of State John Kerry waves as he boards his plane. (AP Photo/Jacquelyn Martin, File)

Prior to this one, his longest trip was around 31,900 miles last fall, when he visited East and West Africa, Saudi Arabia, Switzerland, and then flew east to Bangladesh, India and on to China to join President Obama for a G20 summit.

Using a calculator from CarbonFootprint.com, which bases its data on conversion factors from the Environmental Protection Agency, Department of Energy and equivalent agencies in Canada, Australia and Britain, a first-class passenger flying the distance of Kerry’s current trip would be responsible for roughly 16.57 tons of CO2 emissions.

Kerry’s round-trip flight from New Zealand to the Antarctic was aboard a C17 Globemaster military cargo plane, rather than the official Boeing 757 he is using for the remainder of the trip. The two aircraft are roughly the same size and the latter’s engines are based on those used by the 757.

Kerry has now visited more than 90 countries on seven continents. Last December he broke former Secretary of State Hillary Clinton’s record of 956,733 travel miles during her Jan. 2009-Jan. 2013 tenure.

As of the end of October – the latest figures provided by the State Department – Kerry had traveled 1,327, 715 miles, or almost 53 and a half times around the Earth.

Figures differ depending on source, but Firmgreen.com and Climatepath.org both say long-haul flight produces 0.39 pounds of CO2 per passenger mile. (Long haul flights account for lower emissions per passenger mile, they say, because a high percent of fuel use and emissions occur during takeoffs.)

Based on that figure, Kerry’s travel up until the end of October produced some 234.9 tons of CO2 – more than 14 average Americans will produce over the course of a year.

Speaking Sunday in Wellington, New Zealand before flying to Oman via Singapore, Kerry sidestepped an invitation to speculate on what a Trump presidency would mean for the campaign to combat climate change.

But he delivered a robust defense for the need for ambitious action against climate change, which he said “the world’s scientific community has concluded … is happening beyond any doubt.”

Kerry said the Obama administration would do everything possible until it ends on January 20 “to meet our responsibility to future generations to be able to address this threat to life itself on the planet.”

“We will wait to see how the next administration addresses this, but I believe we’re on the right track,” he said. “And this is a track that the American people are committed to because the majority of the American people believe climate change is, in fact, happening and want to see us address it.”

A Pew poll last month found 48 percent of adult Americans say climate change is occurring mostly due to human activity, 31 percent say it is due to natural causes, and another 20 percent says there is no solid evidence of global warming.