Jessica Robertson: Hello and welcome to USGS CoreCast, I'm Jessica Robertson. Today's CoreCast is the first of a three part series on recent USGS-led reports on climate change which were developed under the US Climate Change Science Program. The report we will be discussing today focuses on past climate variability and change in the Arctic and high latitudes. Temperature change in the Arctic is happening at a greater rate than other places in the northern hemisphere and this is expected to continue in the future. A new scientific synthesis of past Arctic climates demonstrates for the first time the pervasive nature of Arctic climate amplification.
Today, I'd like to welcome and introduce you to our guest, USGS scientist Joan Fitzpatrick, who was the agency lead for this report. Thank you for joining us today.
Joan Fitzpatrick: Thank you for inviting me to do this, Jessica.
Jessica Robertson: First, can you provide us some background information and an overview of this report?
Joan Fitzpatrick: Sure. This particular report is a synthesis of what's currently known about past climate history of the Arctic. Specifically the report focuses on the past history of temperature and precipitation changes in the Arctic, changes in the Greenland ice sheet, past rates of change and changes in sea ice.
Now, the focus on past rates of change is actually shared with the single topic of another one of the USGS led reports, which is entitled "Abrupt Climate Change". This report is one of 21 climate reports that were commissioned in the strategic plan of the US Climate Change Science Program or CCSP.
The general purpose of these reports is to provide the nation's policy makers with in-depth assessments of specific topics in climate change that touch upon the national interest. They cover a broad diversity of topics, everything from the impacts of climate change on agriculture and land and water resources and biodiversity to the strengths and limitations of climate models. The USGS has a lead responsibility for three of these assessment reports.
Jessica Robertson: And what were the key findings of your report focusing on past climate variability in the Arctic?
Joan Fitzpatrick: Well we had key findings related to each of our four technical areas. For Arctic amplification we found that this process - which is the process by which the high northern latitudes respond more intensely to hemispheric or global climate changes - has been a pervasive feature of the earth's climate system for at least the last four million years during both warming times and cooling times. Therefore we can anticipate that continued warming at mid latitudes will result in even more warming in the Arctic and that this will lead to continued increases in glacier and ice sheet melting, coastal erosion, permafrost degradation, loss of summertime sea ice and all of the downstream impacts associated with that.
For the sea ice findings we found that, taken together, when you look at both the size and the speed of the current loss of summer sea ice over the last few decades, it's really very unusual compared to the events in the record from the previous thousands of years, especially when you consider that changes in the earth's orbit over the same period of time, have really made sea ice melting less and not more likely.
For our Greenland ice sheet segment, we determined that sustained warming of at least of a few degrees - more than about 4°F and up to about 13°F - above average 20th century values is likely to be sufficient to cause the nearly complete eventual disappearance of the Greenland ice sheet. This of course would raise sea level by several meters.
Our rates of change finding is that the current rates that we're seeing now of human influenced Arctic warming is comparable to the peak natural rates that are documented by reconstructions of past climates. However, we do know that there are some projections of future human-induced change that actually will exceed the documented natural variability.
Finally, for our rates of change segment, we find that the past tells us that when thresholds in the climate system are crossed that climate change can be very large and happen very quickly. We can't rule out the possibility that human- induced climate change could potentially trigger such an event in the future. And I'd refer your listeners to the assessment report on "Abrupt Climate Change" that was recently also published by CCSP for more information on this.
Jessica Robertson: Now, why exactly did you focus on the Arctic? What's the significance of this area?
Joan Fitzpatrick: Jessica, the Arctic has very strong feedback mechanisms that act to multiply the effects of overall hemispheric or global temperature changes. These are the source of Arctic amplification itself - the phenomenon itself. The presence of a highly reflective insulating snow and ice cover, the existence of a large body of land ice (that is the Greenland ice sheet), the existence of perennial and seasonal sea-ice cover blanketing the Arctic ocean and insulating it, the existence of extensive permafrost, the fresh water input balance and ocean circulation - these all factor into the Arctic's enhanced capability to both respond to and to, of itself, drive the global climate system.
Jessica Robertson: And what does this report tell us in terms of future research needs or whether we should prepare for Arctic changes?
Joan Fitzpatrick: Well of all the 21 climate synthesis reports this is the only one that really focuses specifically on the past record of climate. Our current understanding about the earth's climate system operates is grounded in our computational models. And these models are based for the most part on what we understand about how climate works based on the very short period of time that mankind has kept instrumental records, which is about the past 250 years. I tell people this is a little like trying to understand the plot of "Gone with the Wind" from watching about the last two seconds of the movie.
We need all the robust paleo-records we can get in order to build up a coherent picture of the range of natural climate variability, the mechanisms that drive these climate changes, specific regional responses to global climate forcings, the conditions under which abrupt change can occur, and the ecosystem level impacts and responses to these climate changes.
A more comprehensive understanding of the plot of the movie, if you will, helps us to design even more robust predictive climate models. It'll help us design effective monitoring strategies and it'll really allow us to begin to contemplate effective strategies for adaptation and mitigation.
Jessica Robertson: Joan, your response really shows how the importance of climate models can hardly be overstated. They really form the fundamental basis of our entire understanding of the earth's climate system. And I see what you're saying that in order to continue to expand our understanding and continue to enhance these models we really need to be able to explain past conditions as well. So can you tell us how the report's conclusions were drawn?
Joan Fitzpatrick: Sure. The synthesis itself was drawn from the existing literature on Arctic paleoclimate covering the past 65 million years. We focused on the last 65 million years because this is really about the extent of the span of time that we can make a reasonable case that conditions now in terms of oceanic gateways and continental positions are not so drastically different now from what they were 65 million years ago. So that's why we drew the line at about 65 million years.
Over that period of time we looked at everything from lake and ocean sediment records, ice cores, tree rings, pollen and vegetation records, fossil assemblages, biogeochemical markers, insect records, and geomorphic features like sand dunes, coastal terraces, moraines and other periglacial features. Records from Bowhead whale bones, ice rafted debris, driftwood, marine trough, mount sediment sands and the list goes on and on. So we covered a broad, very extensive range of kinds of records or proxies. We had 37 contributing authors from five nations and it was a two-year long effort to produce this report.
Jessica Robertson: Sounds like a very robust process. And looking back 65 million years is very impressive. From your perspective, can you share with us the most interesting part of this research?
Joan Fitzpatrick: Well for me of course the opportunity to work with some of the best minds in paleoclimatology was a really rewarding experience. For the group as a whole, I think the opportunity to take a really integrated look at the entire Arctic over this period of time highlighted for us how strong the regional variability in the Arctic is and hence the potential peril there is in over interpreting any one single record originating from any one sector of the Arctic.
The report also brought home how much we need sediment course from the Arctic Ocean to really help extend our understanding of sea-ice behavior. This area of research is really just now beginning to get some serious traction with the newest cores that have been recovered within the last few years from the Arctic basin. I anticipate exciting new results are going to come out of these new records.
Jessica Robertson: And is there anything else you want to share about this report?
Joan Fitzpatrick: I wanted to let your listeners know that I thought this was a great example of how strong partnerships between federal and academic sectors can really meet the larger needs of both. The four technical chapters of the report are going to appear as a thematic set of papers in a juried journal by the end of the year. During the course of compiling the assessment there was a strong effort made to try and quantify Arctic amplification as well, based on the paleorecord. This to is going to appear on scientific literature soon.
In all of this, the overarching federal need to provide the best science possible to help inform the decisions the policy sector have also been fulfilled. So the way the whole thing proceeded really met the needs of both communities very well.
Jessica Robertson: Well thank you for joining us today. And thank you to all of our listeners who joined us for this episode of CoreCast. Don't forget to listen to our upcoming CoreCasts on the other two USGS led reports under the US Climate Change Science Program. Those reports focus on the potential for abrupt climate changes in the 21st century which would pose clear risks to society in terms of our ability to adapt and climate changes to ecosystems and resulting responses including insect outbreaks, wildfire and forest dieback which are not easily reversible.
If you'd like to know more about this report and other CCSP products, visit www.climatescience.gov. The report discussed today is Synthesis and Assessment Product 1.2 "Past Climate Variability and Change in the Arctic and at High Latitudes".
As always, CoreCast is a product of the US Geological Survey, Department of the Interior.
Temperature change in the Arctic is happening at a greater rate than other places in the Northern Hemisphere, and this is expected to continue in the future. As a result, glacier and ice-sheet melting, sea-ice retreat, coastal erosion and sea level rise can be expected to continue.
USGS scientist Joan Fitzpatrick discusses a new report on past climate variability and change in the Arctic.