Tag Archives: climate change

Jet Streams

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Resolute Bay, Canadian Arctic, winter 1990

The Polar Vortex. Sounds like scenes from the apocalyptic movie The Day After Tomorrow; a bit of a down-draft and everything freezes. The real vortex refers to a low-pressure system with a cold, west-to-east flowing (counter clockwise) air mass that hovers over the north pole (there is also a vortex over Antarctica). When stable, the cold air remains in the north, contained by the polar jet stream. When unstable, as sometimes happens in winter, the polar jet stream meanders such that cold air can penetrate much farther south.

February is deep winter in the Arctic, and yet current temperatures there are hovering around zero degrees C; almost T-shirt weather.  Warm air masses are being allowed to enter this normally frozen domain, while the cold snaps (March 2018) are wedged into southern Canada, USA and Europe. Arctic winter temperatures are abnormally high, significantly higher than past recorded temperature anomalies.  Is something happening to the Polar Vortex; is it in a state of decay? And if so, is this process part of some long-term climate change, or is it just another anomalous spike on the climate record? None of the answers proffered so far are definitive, at least from a scientific point of view (mind you, the media are having a field day). Science will go some way to resolving this problem by observing how jet streams respond over the next few decades. Continue reading

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It looks like sea level rise is accelerating; the era of satellite altimetry

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Strand Fiord, Axel Heiberg Island.

Sea level. It’s the most common starting point for any kind of elevation measurement, a datum, that for centuries was understood to be an invariant surface. Then some geologists came along and showed that, for eons past, sea level has risen and fallen countless times; coasts were flooded, sea floors exposed. And sea level is still changing, going up in some places, down in others, but on average it is rising; it has been doing this for the last few 1000 years.

The current globally averaged rate of sea level rise is 3.0 +/- 0.4 millimetres per year, based on satellite altimetry. Satellite measurement of sea level is now about 25 years old. Earlier measurements, some dating back to 1700, were made by tide gauges, basically glorified measuring sticks (the initial technology was just that) which over the years, have become sophisticated, automated measuring systems.  Tide gauges measure water levels on a local scale, and in order to make sense of the data in the context of global sea level, all manner of local variables need to be considered: for example, is the location open to the ocean or a sheltered harbour, storm surges, seasonal changes in currents and water mass temperatures, changes in air pressure (sea levels rise during passage of low pressure systems – this is part of the storm surge), and whether the land is rising or subsiding (i.e. local tectonics). In contrast, satellite altimetry gathers data from a much broader swath of the ocean surface. Both Jason 2 and the more recent Jason 3 satellites can cover 95% of the ice-free ocean surface in 10 days. The accuracy of the Jason 3 radar altimeter is currently an impressive 3.3 cm.

 

Sea level anomaly maps for 2016, from satellite dataRising sea levels and changing climate are inextricably linked because ocean water mass volumes increase or decrease in concert with changes in the volume of land-based ice (primarily the Antarctic and Greenland ice sheets), plus changes in ocean temperature (this is the steric effect) and salinity.  Thus, if there is an acceleration in atmospheric warming or cooling, there will be a reasonably sympathetic acceleration in ocean volume change and therefore, sea level change.  This is the scenario posited by many climate-change model projections – that increased warming will produce an acceleration in sea level rise. A recent publication that analyses the 25 years of satellite altimetry data (Proceedings of the National Academy of Sciences, 2018), concludes that the (global) average sea level rise is accelerating at 0.084 +/- 0.025 mm/year2, which means that the current speed of sea level rise (about 3 mm/year), will increase year upon year.

 

Sea level curves for 1993 to 2017 showing the steric and volume contributions

The possibility of accelerating sea level rise during the 20th century, based mainly on tidal gauge data, has been debated although most analyses indicated a degree of ambiguity in the data. In fact, a 1990 ICCP report (page 266) concluded there was little concrete evidence at that time for an acceleration, although re-analysis of 20th century tide gauge data, published in Nature (2015) did show a possible accelerating trend. If that analysis is correct, this is the first time such an acceleration has been demonstrated with reasonable confidence from a single data set.

As the published analysis shows, teasing accurate sea level numbers from the satellite data is not a simple task.  As is the case for any kind of remote sensing or monitoring, there are data corrections and filters.  Some of the corrections include:

  • Terrestrial water storage (rivers, lakes, and groundwater); this is necessary because of natural variability in the exchange between land-based water and the oceans,
  • Natural variability in land-based ice storage and melting, that adds to, or subtracts water from ocean masses,
  • Natural variability in heat exchange between the atmosphere and oceans (the steric contribution to sea level),
  • Multi-year cycles such as ENSO (El Niño Southern Oscillation)
  • One-off events such as volcanic eruptions that affect regional temperatures because of ash and aerosols; in this case the Pinatubo eruption influence was incorporated into the analysis.
  • And the drift in satellite orbits; this variability is much less than that of tide gauges.

The sum of these errors gives the plus (+) and minus (–) value (0.025 mm/year2) that is attached to the overall result – 0.084 mm/year2 (check the open access publication for details). So, if our current rate of sea level rise is 3mm/year, then in 10 years the rate will have increased (accelerated) to 3.84 mm/year, and after 50 years to 7.2 mm/year (almost double the 2017 rate).

Data correction may seem like a bit of a fudge, but it is a critical part of almost every measurement we take, no matter where or what it is; it is part of the process in science that makes data intelligible and coherent.  Correcting data is part and parcel of any attempt to isolate causes and effects, as well as determining the kinds of error that are inherent in all measurements. The bottom line in this example, and one that is pointed to by the authors, is that the analysis is preliminary, and that some of the corrections might change as our knowledge of climate and other global systems improves.  However, there is confidence that this kind of analysis is on the right track.

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So, adding CO2 does increase surface heating; how science has filled another gap in our knowledge

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Read any scientific paper or blog on climate and you’re bound to come across the phrase radiative forcing.  Radiative forcing is central to all climate science. Radiation from the sun heats our atmosphere and earth surface.  Some of this radiation is reflected back to space. If there is a balance between incoming and outgoing radiation then average global atmospheric temperatures neither increase or decrease. However, if the balance is perturbed, climate will warm or cool. Radiative forcing causes climate imbalances.  Thus, volcanic aerosols tend to cool things off, decreasing albedo will tend to warm them. Continue reading

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Volcanism does not cause glaciations; let’s turn this statement on its head

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Is there a relationship between volcanism and glaciation?

It is almost a truism that volcanic eruptions influence climate. Cold winters and even failed crops, particularly in the northern hemisphere, followed on the heels the Tambora, Krakatoa, and Pinatubo eruptions.  But these climate aberrations were relatively short-lived, counted in years; the stratospheric aerosols and fine volcanic ash that reflect solar radiation back into space, eventually succumb to gravity and fall to earth.  Eruptions of this kind do not result in long-lived, or permanent changes; they are temporary blips on an evolving earth and an evolving climate. Continue reading

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CO2 – the Good, the Bad, and the Indifferent

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CO2 has a bad rep.  We can’t do without it (GOOD – it’s part of the photosynthetic process), but it looks like we’re upsetting the balance between having too little and producing too much (BAD).  I take some of the blame for this: I drive a car (out of necessity), run a small boat (that I really enjoy), use a gas stove (the best cooking device ever), use a couple of lawn/orchard mowers (also necessary to keep the weeds at bay in our organic kiwifruit orchard), and take trips to Canada and beyond (which is life-affirming).  I guess we all have our crosses to bear (INDIFFERENT), but I do take solace in the knowledge that my carbon footprint is more than offset by the biomass on my organic orchard.

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The crosses I bear

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I have had occasion recently to bear the brunt of criticism about some of the decisions one makes in life.  These comments, made during a discussion on climate change, were a polite but thinly veiled criticism of some of my choices about where and for whom I had worked over the past 4 decades.  I was given to understand that working for oil companies (mainly offshore Taranaki) and mining companies (NZ, Chile) was a blight on my character; how could I talk sensibly about climate change science when I was one of the main contributors to the world’s problems.  That I had assuaged my conscience by also working on groundwater and geothermal projects (renewable), CO2 sequestration,  teaching and research seemed irrelevant.  I had given in to the dark side.

I’ve had discussions like this on several occasions and as with them, little was resolved during this particular discourse. But I did feel annoyed.  The phrase “but you had choices” and something about selling of souls had been trotted out two or three times during the chat, and it was this insistence that grated most.  Choice, it seems is a convenient crutch on which to foist an opinion.

There are plenty of everyday choices which are obvious: what to have for dinner, who not to vote for.  These kinds of choices are explicit and for the most part reasoned.  But there are also choices that, while not necessarily unconscious are hidden, or if not hidden then conveniently tucked away lest they become uncomfortable.  Discussions about renewable resources, climate change and environmental issues are good examples where our efforts to be responsible citizens (and scientists) can begin to unravel if we take too much notice of these hidden choices.

Consider the following – you are going to a conference.  Here is a list of a few inconvenient but inevitable choices you will make:

  • You will need to travel (car, plane, train). Every step of this journey will require the use of fuels, plastics, metals, food, clothing, communications (the list goes on). Hydrocarbons will be front and centre of virtually everything that gets you from A to B.  Would you choose not to attend the conference because of the carbon footprint?  Most will feel some guilt but attend anyway, either ignoring the issue or designing some arcane explanation involving necessity.
  • Accommodation (same kind of list)
  • Most people at the conference will have at least one form of communication – phone, tablet, laptop (plastics, metals, including rare earths). Tweeting directly from a conference is now common place. But will any thought be given to the atrocious working conditions under which some foreign governments and mining companies extract the rare earth metals used in these devices?

There may of course be arguments that the improvements to society and science that someone makes by going to the conference (or to the office, the lab, the field, home) is worth the sacrifice of a few dark choices. Or that some choices are worse than others. But this is a pretty self-serving and unnecessary position to take. I doubt there would be many who would begrudge the scientist traveling to Antarctica to collect data that improves the veracity of climate models.

I now feel vaguely vindicated. My soul is largely intact. I have played my part in providing the wherewithal for conference goers and field trippers. In the end whatever tasks I might have undertaken for the dark side, were no better or worse than the crosses that our conference goer and field scientist have to bear.  As Jane Austin’s Mr Bennett said “I will get over it and probably more quickly than I should.”

I also have faith in science’s and society’s ability to find solutions to many of these unfortunate choices.  I expect it will be a gradual process.  Yes, we can learn to recycle, locally, our old cell phones, and purchase electric vehicles when they are reasonably priced and when there is sufficient infrastructure.  But in the meantime most of us will still need to fill the petrol tank or hop on that plane.  If climate change is a reality (and there seems to be a consensus that it is), then so too is the length of time it will take to make the necessary structural changes to the way we live.  In the end, moral indignation at these darker circumstances seems neither fair or useful.

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The Bubbles That Changed our Perspective on the World’s Climate

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Camp water supply from a small pond on this iceberg

One of my geology field seasons in the Canadian Arctic worked out of a base-camp on Axel Heiberg Island (west of and snuggled against Ellesmere Island).  It was the spring thaw and all rivers and streams were muddy.  Our only source of clean water turned out to be a small melt-water pond atop an iceberg in Strand Fiord, a few hundred metres offshore.  The helicopter would make daily trips with a 45-gallon drum to collect the water.  The ice and its water were crystal clear and probably a few thousand years old. It was a treat. Perhaps the only thing missing was the occasional Scotch or G&T. Continue reading

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Geological Trappings; Carbon Capture and Storage

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CCS – what is it?

Carbon dioxide is a significant by-product of oil and natural gas production at the well-head, hydrocarbon and coal combustion (especially in power generation) and several manufacturing industries (e.g. cement).  Carbon Capture and Storage (CCS) involves technology that captures CO2 produced by these industrial processes and stores it underground.  In doing so, CCS technology attempts to prevent the CO2 from being released into the atmosphere.  From the point of view of potential climate change it seems like a sensible thing to do.  However, CCS does have its detractors who argue primarily that either it doesn’t matter how much CO2 enters the atmosphere, or that the costs far outweigh the benefits.  Indeed, the cost of CCS programs is high.  Regardless, the science of CCS is fascinating. Continue reading

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Sea-Level Change; Busting a Few Myths

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So you think sea level is the same everywhere!

Canon Fiord, Arctic Canada

Canon Fiord, Arctic Canada

Climate change predicts that sea levels will rise at an increasingly rapid rate.  Some of NASA’s new satellite altimetry data hints that this is already happening.    There is a multitude of voices crying out for government planners to prepare for inundation of vulnerable coasts.  Small island states are particularly at risk.  Forward planning would certainly be a wise move.  If average sea level rises say a metre in the next 100-200 years many coasts will be inundated and storm surges will push farther inland.  Forward planning does make sense. Continue reading

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