Sea Level Rise: Why We Care, Part 1

Just a few weeks ago we published an updated sea level assessment for Washington State, for which I was the lead author.  We anticipated a small splash when we released our assessment, and indeed were covered in a variety of print, radio and TV outlets:

Along with that coverage came a smattering of emails from people around the state, most of them just from individuals, and some appreciative, some dismissive, and some thoughtful.  One stuck out for me for its honest skepticism:

"With all due respect, how do we know that this is not fake news? I think a lot of us out here are very skeptical of this kind of reporting and these studies because we don't understand what it's based on and bias."

We intentionally didn't dive too deeply in our report into the basis for the concept of climate-driven sea level rise - that wasn't the purpose of the document.  However, I figured I would at least take a crack at starting to address the question implicit in the comment above on this blog.  I frame that question as follows:  "Why is sea level rise a thing?  We have enough stuff to worry about, so why should I care?"  The full answer to this question is well beyond the scope of this blog, and my expertise.  There are probably hundreds, if not thousands, of papers that, together over decades, put together the full story of the connections between greenhouse gases and changes in sea level, but the story that I'm going to tell in multiple parts is my simple way of thinking about that question.

It starts here, with the concept of climate change driven by greenhouse gases.  As many have pointed out, from a geologic standpoint this isn't a new thing.  Greenhouse gases have apparently changed the Earth's climate on multiple occasions in the planet's history.  The primary culprit in most (or all??) of those cases, though, wasn't human emissions, but rather large volcanic flows.  Starting a few centuries ago, though, humans started transferring buried carbon from underground, back into the atmosphere, via coal mining, and then the extraction of oil and natural gas.

There were a few observers in the late 1800's and early 1900's that put together the pieces.  The key insights about the heat-absorbing properties of carbon dioxide, water vapor and other greenhouse gases were made by John Tyndall and reported in 1859 (the story of which is wonderfully recounted here).  These observations of the properties of atmospheric gases provided evidence to support hypotheses about a "greenhouse effect" on Earth originally posed in the 1820's by Jean Baptiste Joseph Fourier.  It didn't take too long for someone to make the connection between the properties of gases that John Tyndall described, and the mining of coal that started in earnest in the 1800's...and indeed in 1896 Svante Arrhenius published a paper describing how changes in carbon dioxide concentration in the atmosphere should lead to changes in temperature on the ground.

To me, these early insights about gases and the global system lay the groundwork for two fundamental ideas that, based on their insights, I trust:

1)  The idea of climate change - that greenhouse gases can control, or change, the Earth's climate

2)  That humans are capable of adding those greenhouse gases to the atmosphere via extracting fossil fuels from the ground, and transferring the carbon they hold to the atmosphere.  Its not just volcanoes that can do that.  

From there, rather simply put, the rest is details.  How exactly does carbon move through the Earth system after it is added?  How long does it take for geologic processes to remove carbon?  How much does the ocean absorb?  How much does adding a certain amount of different greenhouse gases to the atmosphere change temperature?  Where and why are there differences around the globe?  How much of warming that we observe is due to greenhouse gas emissions, versus "natural variability"?  The list goes on and on.

There are highlights along the way.  In 1958 Charles David Keeling began to focus on monitoring carbon dioxide in the atmosphere, and his efforts are on-going to the present day:

and clearly demonstrate a trend in carbon dioxide concentration in the atmosphere.  

Also in the 1950's, the development of micro-processors started to lead to rapid advances in the ability to model processes related to Earth's climate, and in the 1990's led to the development of global climate models, which are now widely used in efforts to translate scenarios of future emissions changes into estimates of future greenhouse gas concentration, temperature change, and a slew of other climate impacts.  Climate models are complicated, imperfect and most definitely aren't my expertise, so I find these sorts of layman descriptions helpful:

Climate models, there use, short-comings and applications are probably the key source of confusion about climate change, and perhaps rightly so.

The 1990's and early 2000's marked the emergence of climate assessments - efforts to review, sort, rank and summarize scientific developments about climate change and its associated impacts.  Early on these processes were international, and more recently national, regional and local, and also associated with mitigation or adaptation planning processes.  

I will stop there for now...and we haven't even yet touched sea level.  That is coming up next.  My key take-away from this Part 1, though, is that there is a real basis for the concept of climate driven forced by humans.  There certainly is real and honest debate about the details, but we will start Part 2 with that concept.