Tag Archives: Carbon dioxide levels in atmosphere

CLIMATE CHANGE

9 Mar

When William Speirs Bruce planned his 1902-1904 expedition to Antarctica his primary ambition was science, as opposed to exploration.

In 1903 he built two scientific observatories on Laurie Island on the northern edge of the Weddell Sea. This was the start of a collection of scientific records that was continued, when Bruce left the Weddell Sea, by the Argentine. Recordings have now been made for 116 years. They continue today providing unique information about meteorological, magnetic and oceanographic conditions in Antarctica.

In relation to meteorology, this graph running from 1903 to 2020 shows the trend and variance in the mean annual temperature on Laurie Island. It is by far the longest recording of temperature in the region (the second longest being from Argentine Islands off the Antarctic peninsula which runs from the early 1950s). As can be seen there is a trend in temperature from – 5°C to -3°C. The graph also illustrates clearly the variability in the annual records, but it is clear that the twenty-first century recordings approximate to the upper recordings in the early 1900s.

This graph would never be available save for William Speirs Bruce’s foresight in encouraging a network of weather stations to be run continuously in the South Atlantic.

 

World temperature is rising, controversy persists, though not amongst the scientists, as to how much man is contributing to the problem.

The reason there is life on our planet relates to infra-red active gases (carbon dioxide, methane, water vapour that are in the stratosphere). The lack of these gases would result in a significantly colder climate, a permanent ice age. Conversely, a rise in infra-red gases would result in a rise in temperature, though there is a complex, non linear relationship between small changes in carbon-dioxide, methane and other trace gases, and the consequent temperature rise. The global climate system is complex which makes it difficult to simply ascribe cause and effect.

But carbon dioxide levels do have a strong correlation to mean global temperatures. Fascinating ice core records were first recovered from the Russian station Vostok which provided records covering 450,000 years. More recently a record of 800,000 years has been recovered from “Dome C” in Antarctica (part of The European Project for Ice Coring in Antarctica). This shows, very clearly, the link between temperature and carbon dioxide levels over cycles of glacial and interglacial periods of around 100,000 years. This is a natural process linked to long term small variations in the Earth’s orbit and axis of rotation. The level of CO2 in the stratosphere has varied naturally between around 180 ppm during glaciations to 280ppm in the warm interglacials, as shown in the records.

                        It has now passed 408 ppm.

Carbon is ubiquitous, in fossil fuels (oil, natural gas, coal), in organic matter in soil and in rock, in the sea. Carbon dioxide is emitted when we exhale, When fossil fuels, are burned carbon dioxide is produced. In 2019 the global emission was 33 gigatons (a gigaton is one billion ).

In the oceans it is estimated that there are billions of metric tons of carbon and further billions of metric tons in sediments on the sea bed. The latter comes from the shells of marine creatures that have absorbed carbon from the water, sunk to the ocean floor and later formed sedimentary rocks.

A raised carbon dioxide level relates to a rise atmospheric temperature which in turn is associated with a rise in ocean temperature, seawater expansion and a rise in water level. The increased water levels are also contributed to by melting land ice and erosion of ice shelf bases. Ice shelves hold ice from flowing outwards and thinning of these shelves increases the flow of ice seawards. An estimated ice loss across the entire Antarctic continent was 43 gigatons each year on average from 1992 to 2002. The loss has accelerated between 2012 to 2017.

Potential results of sea-level rise are coastal erosion and damage. Subsequently, inland areas would become affected and the soil contaminated. If the rise continues toward one metre, some of the world’s major cities will come under threat and even low-lying countries such as Bangladesh, will be threatened.

Ocean acidification, due to dissolved carbon dioxide, has serious consequences.

Acidification affects the southern Krill population. Krill, an essential primary food source, are small crustaceans that feed on zooplankton and convert this into a form suitable for larger animals such as whales, seals, penguins, squid, and fish to eat. All Antarctic wildlife ether depends on krill or depends on something that eats krill for survival. Without this stable base, the food chain linking upwards would deteriorate and eventually collapse. In addition, cold-water corals, which have calcium carbonate in their shells, become less able to build their shells and breeding grounds for both fishes and mammals would be lost.

But some do not subscribe to the concept of global warming, for example: Donald Trump cast doubt on a U.S government report warning of the devastating effects of climate change. When he was asked if unchecked global warming would wreak havoc on the US economy, he said: “I don’t believe it.” The administration has pursued a pro-fossil fuels agenda.

But if conclusions such as this from the U.S. President are wrong, the price to pay is huge. Given the persistence time of CO2 in the stratosphere of 100 years, even if the world were to stop all emission now there is still that legacy which is likely to take the planet past the 1.5 degrees C warming, which scientists say we should not pass. Currently carbon emissions from fossil fuel burning are steadily rising, rather than decreasing. Scientists warn that we are playing dice with the future of humanity.

A final point – global human population increase. This is approximately 83 million annually, or 1.1% per year. Population numbers have grown from a billion in 1800 to approximately 7.616 billion in 2018. Improved medical care and reduced child mortality would be a powerful incentive for families to have the confidence to limit the size of their families.

Policies now direct to keeping carbon emissions flat until 2050. But so far there is little sign of sufficient practical action on this. Scientists are now increasingly coming to the conclusion that we need to go “carbon negative”, which raises the possibility of large scale “geo-engineering”. – Geo-engineering is defined by as the large-scale manipulation of a specific process central to controlling earth’s climate, for the purpose of obtaining a specific benefit (Britannica .com).

Millions now do understand the dangers of global warming and the urgency to contain it. Humanity is at a crossroads, for the sake of our grand-children we need to make the right turn.

 

With grateful acknowledgement for the comments by John Dudeney O B E.-  my co-author of ‘William Speirs Bruce, Forgotten Polar Hero’