Friday, May 19, 2017

Water, Water Everywhere (At Least Everywhere It's Not Wanted)

Let's cut to the chase. The IPCC, Intergovernmental Panel on Climate Change, has estimated sea level rise over the course of this century will be somewhere between 30 cm. to 1 metre. With the IPCC's track record for getting it wrong, understating the pace and impact of climate change, you can consider that a low ball opinion.

More recent studies of the rate at which ice caps in both hemispheres are declining suggests by 2100 we'll see between 2 and 3 metres of sea level rise. With the current rate of sea level rise of 4 mm. annually and increasing, 2 metres is probably a safe bet.

Which lends a bit of perspective to the recent study about near-term sea level rise. Here they're looking at sea level rise of 5, 10 and 20 cms.  That sort of rise may not be devastating in its own right but it can be when it combines with high tides and storm surge events and it's expected to cause havoc in the tropics first.

In those locations, just 2.5cm of sea level rise leads to extreme water levels being seen twice as often, while a 5-10cm increase means coastal floods are twice as likely across all the tropics. A rise of 20cm leaves almost every coast with twice the risk.

The rise of 5-10cm, likely to occur within a couple of decades, would mean major cities including San Francisco in the US, Mumbai in India, Ho Chi Minh in Vietnam and Abidjan in Ivory Coast facing a doubled risk of coastal floods. “The maps of increased flooding potential suggest a dire future,” write the scientists.

“This study shows how even small changes in mean sea level can significantly increase the frequencies with which critical thresholds are exceeded,” said Thomas Wahl, professor of coastal risks at the University of Central Florida, who was not part of the research team.

While coastal British Columbia is obviously not in the tropics it already experiences seawater inundation events, especially in spring, when high tides and storm surges can be compounded by early season mountain snowcap melts and runoff. British Columbia's Lower Mainland, one of the most densely populated regions in Canada, is particularly vulnerable when meltwater runoff swells the Fraser River as it nears the sea. There are some very low-lying municipalities along the way, Richmond and Surrey in particular.

[University of Illinois prof, Sean] Vitousek said: “We are going to have to [cut carbon dioxide emissions] and engineer the coastlines to stop a lot of these events from happening. We want Greenland and Antarctica to remain as ice for as long as possible.

“One metre of sea level rise is going to be a game-changer for the coastal zone. The next time you are at the beach or down by the water, think about what that area would be like in some of these sea level rise scenarios, half a metre or metre. You’ll see it’s a pretty scary proposition.”


Owen Gray said...

It's been a very wet spring here, Mound. Carp have been swimming in the streets of Belleville. Even the dullest among us should be able to figure out that something is wrong.

Toby said...

This is not just a coastal problem. Okanagan Lake has risen so much that an old paddle wheel boat is now floating.

When we look at various floods across Canada we find some people stating that they have never had flooding as long as they lived there. Lakes, rivers, streams and water tables are rising to levels people have not seen.

The Okanagan has a semi arid climate yet local plumbers are doing a booming business installing sump pumps.

The Mound of Sound said...

Yes, Owen, even the dullest among us. Sadly that doesn't seem to include Justin or Cathy or Rachel or Christy or the fossil fuelers of Western Canada.

The Mound of Sound said...

Toby, sea level rise is a coastal problem. Inland regions have their own flooding problems but that's not driven by sea level rise.

Powerful changes - a warmer, more humid atmosphere; changes to the jet stream circulation; atmospheric rivers all point to a broken hydrological cycle globally. What most don't understand is that the gentle hydrological cycle of the Holocene facilitated agriculture to the level needed to grow our numbers from 1-billion around 1814 to today's 7.5 billion. Imagine a sevenfold+ increase in just two centuries. What could possibly go wrong?

Toby said...

Mound, while there are some technical differences between coastal and inland flooding you won't persuade anyone with a basement full of water that those differences matter. What everybody knows about global warming is that sea level will rise. (What will that do to aircraft altimeters? Will Mt. Everest be shorter?) What most people haven't quite figured out is that global warming is changing weather patterns. We are seeing water where we don't expect it and not where we do.