I'm going to start off this presentation with a quick narrative that I generated for a lighting talk I provided shortly after Hurricane Sandy (when people had become especially interested in my field, for obvious reasons.) At 9:30 in the morning on October 29th, 2012 the storm surge of Hurricane Sandy hit New York Harbor almost exactly at high tide. A few hours later (as seen in these pictures) it was high tide in Boston Harbor. Six hours after that the full force of Sandy's storm surge hit Boston. But it arrived at low tide. Nobody even noticed. However, if Sandy's full storm surge had hit Boston at high tide the flooding in Boston would have been similar to the flooding in New York — flooding that caused damage that I would not have wished upon even the most die hard Yankees fan. We'll start this segment by talking about misconceptions regarding climate change. First let's talk about carbon dioxide, CO2, more generally referred to as "carbon.
" It's really carbon dioxide concentrations we're talking about, not carbon. The first misconception that we'll discuss today suggests that carbon dioxide concentrations have always varied and the current trend of increasing concentrations is just part of a naturally varying cycle. So, there's no reason to be so alarmed about CO2 levels, or is there? What's true is that carbon dioxide concentrations have always varied, as we can see from this graph which is based on ice core data. For the past almost a million years carbon dioxide concentrations in the atmosphere have never exceeded a threshold of 300 parts per million. However, the current trend of increasing concentrations is NOT part of a naturally varying cycle. As you can see here, the 2008 observed level of CO2 in parts per million is right around 350. You may have heard of the environmental organization called "350.org;" their name is based on that number.
When you get further out into the future, the modeled projections of carbon dioxide levels in the atmosphere suggest that the level will ramp way up. This chart shows two possible scenarios for the future; a high emission scenario and a low emission scenario. The high emission scenario assumes what I like to call "business as usual." This high emission scenario generally assumes that we do not change our patterns or our life styles regarding emissions of carbon dioxide …. "Business as usual." The low emission scenario effectively assumes a radical change towards a greener life style– solar energy, wind generators, electric cars, etcetera, but that is just not happening today. On a global scale, we continue to do "business as usual." So the high number is a more likely projection of what we can expect by the end of the century. As of May 2013 we have a current update on CO2 levels and you can see at that point we had hit the 400 parts per million level.
The thing that's interesting about this chart as compared to the prior chart is that the right side of this chart provides a zoom in on the past several decades to that shows the current acceleration of this trend beyond the 300 parts per million threshold. Another misconception suggests that carbon dioxide can't be the problem because is just part of our natural cycle; we exhale carbon dioxide, plants absorb carbon dioxide. The issue here is one of balance on a planetary scale. As you can see on this chart, there are all sorts of processes by which carbon dioxide is absorbed or emitted into the atmosphere, and it indeed is a natural cycle. What's different now is our impact on that natural cycle. Most importantly, since the beginning of the industrial era, we're taking fossil fuel – carbon stored inside the planet for many many eons – and we're bringing it up to the surface and then ..
. we're burning it!! We've upset the balance. A third misconception suggests that there's no evidence that climate change is real and there are a lot of self-proclaimed experts, many of them who are not themselves scientists, promoting this misconception. So, do we really have any evidence that climate change is real? Here are three scientific observations, and there are many others. – Ice caps and glaciers are melting – Sea level rise appears to accelerating, and – We're experiencing extreme weather events of increasing intensity These observations are consistent with what we understand about climate change. The last misconception we'll discuss today, suggest that humans are too small to alter natural systems at a global scale. Let's look at the data that contradicts this misconception. Human kind has converted one quarter of the earth's surface to agricultural. Greater than fifty percent of forests have been converted.
Approximately fifty percent of grasslands have been converted and most of this has occurred since 1950. Since 1969, that amount of water stored behind dams has quadrupled. What we're in now is generally being called the anthropocene (although there's no consensus on this term yet). The anthropocene is generally defined as the geologic era during which humans have begun impacting the planet. So, moving beyond misconceptions into science, I'm now going to cover some findings of the United Nations organization called the Intergovernmental Panel on Climate Change (IPCC), a group with many many scientists. The IPCC 2007 summary for policy makers reported that it was "unequivocal" that the Earth's climate is warming and "very likely" that human emissions are chiefly responsible. Looking at this slide, you see a multicolored bar across the bottom. The bar provides a nice translation the IPCC has developed to provide a bridge between science and policy language.
For example, the IPCC equates the policy term, "very likely" with the scientific confidence level of 90%. In September of 2013, the IPCC released the latest summary report for policy makers. They still find that it is "unequivocal" that the Earth's climate is warming, but in this year's report the IPCC states that it is "extremely likely" that human influence has been the major cause of the unequivocal global warming. Using IPCC translation between policy language and scientific language "extremely likely" equates to a 95% degree of certainty. Let's look at some the critical talking points from the 2013 IPCC report that relate to sea level rise. The 2013 IPCC report states there is "high confidence" that ocean warming dominates the increase in energy being stored in the climate system. Just like a lake or any large body of water, the ocean is a heat sink and has absorbed and is now storing a lot of heat. So what does that mean? Well, image that we decided today to go into what I call 'cave man' mode. We turn off all the lights, live in shack, however you want to define it; just stop using electricity and petroleum fuels.
Stop emitting carbon dioxide. It's not realistic – hence the term "cave man mode." Yet even if we did all that, we would still experience the effects of climate change, including sea level rise, among other effects, because the ocean has stored all that heat and it's going to take a long time to release that extra heat. Other points made by the IPCC include their conclusion that … – The global ocean will continue to warm during the 21st century, and – Heat will penetrate from the surface to the deep ocean and affect ocean circulation The IPCC further concludes that the global mean sea level will continue to rise during the 21st Century and the rate of sea level rise will increase. And that's the key. It's not just a straight line any more, sea level rise is accelerating. And here, are two very important points: – Most aspects of climate change will persist for many centuries even if emissions are stopped. (That's referring to the cave man mode I mentioned earlier), and.
– "This represents a substantial multi-century climate change commitment….." We're in this now. We need to be able to recognize misconceptions about climate change for what they are – misconceptions. And we can do this by learning more about the science about climate change; science that's been well articulated by research organizations such as the United Nations' Intergovernmental Panel on Climate Change..