If the past is any indication of future climate possibilities, we may need to deal with the issue of sea level rise sooner than anyone thought.
Dutton says even if current climate negotiations succeed in limiting global temperature rise to 3.6F that could still be enough to trigger that level of sea rise. Losing them would send ice tumbling to the sea and, after it melted, lapping up against the shorelines around the world.
They discovered this by combining observations from geological records. They have started to awaken – but only barely.
The planet’s other major cache of land ice is Greenland.
So which past periods are a good guide to the present in this respect? The problem with going here by this route is that we’re taking out the ability for humans to prepare or stop what is happening – and are essentially putting ourselves at risk in the long-term for short-term outlooks. The current period is unique because unlike in the past, we’re in the driver’s seat. To really understand what climate change could mean for coastal areas, photos really do the trick. We can’t directly measure things like temperature, ocean levels, or ice sheet volumes.
So what did these eras look like?
More disheartening – at the time atmospheric Carbon dioxide levels peaked at about 280 ppm, while today’s levels are somewhere around 400 ppm. From all of these, it’s possible to build a picture of the climate, the ocean levels, and how much water was locked up in the ice sheets. Sea levels again reached at least six meters above present. Evidence suggests that the Carbon dioxide levels in the atmosphere were identical to today’s levels, but temperatures were between 1 and 4 degrees higher. Sea levels again reached at least six meters above present.
– The third period, 120,000 years ago, witnessed temperatures 1-2 degrees higher than today. Currently, these areas are home to millions of residents.
In some ways, it’s tempting to liken our situation to Marine Isotope Stage 5e – sometimes also called the “Eemian” period – given the similarity of average temperatures.
“What is not as certain is the time frame, which is less well-constrained. We used to think it was centuries”, she said. The study’s findings mean that the planet could be in for major sea level rise even if warming is kept to 2°C – a limit that the world is set to exceed without major action on climate change. Studies from United Nations indicated that the rate of global sea level has intensified since the global warming level doubled in 1990s. The main take-away here is that we don’t know exactly how much sea levels will rise, but they will rise; and we’re causing the rise, through greenhouse gas emissions. Most of the 6 meter figures that seem so dramatic come from the low end of the uncertainty ranges.
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