By Christian Flinn
According to a recent report released by the Proceedings of the National Academy of Sciences of the United States of America (PNAS), sea-level rise over the next century has the potential to bring a coastal city’s fears of being underwater to life. The study, conducted by Benjamin Strauss, Scott Kulp, and Anders Levermann, puts the reality of unchecked carbon emissions in direct – and graphic – connection with how high changes in sea-level rise will be by the year 2100.
The situation, according to the report, is that while many cities like Miami are already seeing the effects of sea-level rise in the form of increased regular flooding and a narrowing shoreline, very few realize the dangers they may face in under 40 years if climate change is not aggressively tackled. Put simply, maintaining current carbon emission levels could cause cities like Miami and New Orleans to be inundated by sea-level rise by 2050, and be completely under water by the year 2100. Emphasizing the critical nature of the situation, the report goes on to say that even if there are dramatic cuts in carbon emissions, cities like Miami will inevitably lose at least 25% of their land mass to sea-level rise. The study, however, does not take into consideration the tremendous advances in technology that are likely to occur during the next 100 years.
Despite this bleak outlook, Dr. Strauss believes that the situation is not completely devoid of hope. “There are a few brighter notes, the biggest of which being that there are a lot of people in South Florida government who are working really hard to deal with rising sea levels," said Strauss. "Our picture of the long-term rise vindicates their work and shows that it's going to be useful and helpful." This is not to say, he emphasized, that Miami will not face significant challenges in the coming centuries, but the greatest opportunity for the city and those like it, is in extending the time frame for sea-level rise for as long as possible.
It is much simpler for scientists to estimate how much ice will melt than to estimate how quickly it will melt. This fact was demonstrated in the report by gathering data from various climate simulations and models in order to answer the question: when, precisely, can a relatively slow and steady rate of global warming trigger abrupt or sudden shifts in particular regions or Earth systems?
Answering this question meant taking the data and using it to determine how often they produced sudden and disruptive changes in the time span of a few decades – or less. The results included 37 scenarios where abrupt changes in global weather patterns occurred, with 18 of them triggered at temperatures just two degrees Celsius from current levels (climate change is defined as two degrees Celsius above pre-industrial temperatures).
According to Sybren Drijfhout, a professor at the Royal Netherlands Meteorological Institute, the value of these results – as dramatic as they are – lies in their seemingly variable nature.
They do not provide insight into the likelihood or time frame of any particular event occurring, yet the report indicates that the main consideration in the case of cities like Miami will be the rate of global warming and how quickly and effectively governments find ways to curb air pollution that accelerates it. This begs a new question: if the models are not indicative of incident likelihood, then how can we be sure that global warming affects them?
The answer is that global warming is the one constant factor that increases the probability that abrupt climate change could occur, regardless of how it might occur. It emphasizes how realistically unstable the future could be; even before reaching the two degrees Celsius point of concern. To further illustrate this point, the researchers involved in the study looked at 37 climate simulations from the U.N. Intergovernmental Panel on Climate Change’s 2013 assessment report of the state of climate science. With projections reaching as far as the year 2100, the simulations indicated several different outcomes of climate change and global warming. Some appeared only once, like a sudden algae bloom in the Indian Ocean, but others, such as the melting – in various proportions – of Arctic sea ice and the partial or full shutdown of circulation in the North Atlantic, appeared multiple times and thus represent a greater cause for concern in the long run.
Returning to the importance of the abruptness of climate change, the above results serve an informational role. They represent scenarios that may occur and, especially in the cases of those predicted to occur below the 2 degrees threshold, are indicative of the unpredictability of climate change and the importance we must place, given that unpredictability, on mitigating and eventually reversing its effects. The report coincides with this finding by stating that planning, technology, and reductions in carbon emissions can delay sea-level rise for centuries, putting the time frame for risk to coastal cities at anywhere between 200 and 2000 years from now.
Miami and other cities like it may use this information to their advantage. Over the past decade chronic flooding and what are known as “King Tides,” especially in low-lying areas of Miami, have become commonplace and are predicted to continue increasing both in frequency and severity. The reasons for this are:
- Tides in the area are naturally higher near the end of summer because warmer temperatures cause water to expand and global warming exacerbates that tendency;
- It is during this time that the velocity in the Florida Current portion of the Gulf Stream is weakest, so water accumulates along the Florida east coast; and,
- It is also during this time that the full moon exerts the strongest gravitational pull on tides in the area.
In response to the King Tides and overall sea-level rise, Miami has adopted a city-wide initiative to improve infrastructure and better prepare for and prevent flooding. The plan, estimated to cost somewhere between $400 and $500 million, disbursed over five years, involves installing 80 pumps around the city and raising roads and seawalls two and a half feet above the ground. The first phase of the project appears to be working but this may be only the beginning of a crucial series of projects that cities like Miami will inevitably have to undertake.
Being one of the richest areas facing the problem, however, South Florida is poised to become a model of prevention for other communities and an example of how best to prepare in advance for sea-level rise.
For more information, contact Christian Flinn at firstname.lastname@example.org.