Action 92. The IPCC 5th Report: read it and (try not to) weep.

At last week’s Climate Solutions event (Action 91), one of the guests asked whether Climate Solutions was interested in responding to the ongoing arguments from climate change skeptics. I greatly appreciated their communication directors’ response, which was to the effect that the debate is over: climate change is happening, it is happening more quickly on many fronts than we even imagined, and there is too much work to be done actually trying to make a difference and rechart our energy course to waste time and effort on the arguments of those who refuse to accept or wish to bury the reality of what is going on.

I totally get that, and I agree; that’s why I am focused on positive, proactive steps that I and we can take to make a difference. However, while I agree that trying to change the minds of the unchangeable is a waste of our time, I do believe there is still an important role to play in talking about the science of climate change. There are still a LOT of people – Im going to venture to say the majority of people- in this country and many other countries that don’t read about climate change, don’t much think about climate change, and don’t care much about climate change. Though that may be changing, especially for those in the paths of superstorms and facing sea level rise, I don’t think any of us can bank on that awareness rising fast or furiously enough to make the changes we need to be making ASAP. And of the subset that are hearing and caring about it, there are many who think of it in an abstract way, or in terms like my daughter’s sitter put it to me last night when I asked her whether they are talking about climate change in our high school, “yeah, we have read some stuff, its really scary.”  For those people who do not know and do not care, we have to keep talking about what climate change is. For those people who do know something about its “scariness” but don’t know what to do about it, we have to talk about it in terms that are honest and real, and we have to talk about solutions and participation.

Climate change is  a massive, complex process that is going to unfold in many ways that are predictable, and many that are not. We understand 400ppm CO2 is linked to large-scale climatological change, and we already see large-scale physical, chemical and ecological responses, but what it is actually doing and at what rate change is occurring,  how it manifests in terms of ice sheet loss, feedback loops, ocean currents, acidification, hydrologic regime shifts, and how all these things vary regionally and locally, still have huge opacities and questions. There are unexpected shifts happening even as we speak; for example, shifts in the arctic ocean food web that are leading to beneficial conditions for some species we perhaps did not expect, and grim circumstances for others— but I’ll talk more about that when I review Dr. Susan Moore‘s talk in an Action to come.

So keeping up with climate science is an important component of the entire fight. As a scientist, I want to have my facts straight, and as an activist, I want to know what I am up against and what can be done. To that end I’ve spent some  time this week reading the Intergovernmental Panel on Climate Change (IPCC)’s Fifth Assessment Report (AR5). The AR5 provides the IPCC’s summary of the current state of knowledge of climate change (full disclosure, I stuck primarily with the Summary for Policymakers, as this provides a great synthesis of much of the research; the full report has all the weeds you could ever need to support the details of the synthesis). These assessment reports began in the 1990s, and have been updated approximately every 5 years, with the AR5 being the most recent version, released this fall.

The AR5 begins:

Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.

And goes on to state:

Human influence on the climate system is clear. This is evident from the increasing greenhouse gas concentrations in the atmosphere, positive radiative forcing, observed warming, and understanding of the climate system.

That’s a pretty clear summation of where the IPCC is at with respect to how they see climate change. Greenhouse gases are rapidly rising,  global climate is shifting,  unprecedented changes are occurring on many fronts, and these rapid changes are manifesting in big ways that include ocean temperatures and volume and major glaciation patterns. And it is clear that human activity is playing a substantial role in many of these major changes.

But it is also important to delve a bit deeper into the details of these changes, to answer questions including, “how fast is this happening”? “Is the earth getting warmer?” “is sea ice completely disappearing”? Answers to these questions include “very fast”, “depends on the scale of your question” and “no, but a lot of it is”. Let’s delve a little deeper into the synthesis report and pull together several of the major findings. Please pardon my edits, but I’m going to bold a few things in here I consider to be pretty darned huge numbers:

  • The atmospheric concentrations of carbon dioxide (CO2), methane, and nitrous oxide now substantially exceed the highest concentrations recorded in ice cores during the past 800,000 years. CO2 concentrations have increased by 40% since pre-industrial times, primarily from fossil fuel emissions and secondarily from net land use change emissions.
  • The ocean has absorbed about 30% of the emitted anthropogenic carbon dioxide, causing ocean acidification.  The pH of ocean surface water has decreased by 0.1 since the beginning of the industrial era (high confidence), corresponding to a 26% increase in hydrogen ion concentration.
  • The IPCC has high confidence that over the last two decades, the Greenland and Antarctic ice sheets have been losing mass, glaciers have continued to shrink almost worldwide, and Arctic sea ice and Northern Hemisphere spring snow cover have continued to decrease in extent.  Annual mean Arctic sea ice extent decreased over the period 1979–2012  in the range of 3.5 to 4.1% per decade (0.45 to 0.51 million km2 per decade), and 9.4 to 13.6% per decade (0.73 to 1.07 million km2 per decade) for the summer sea ice minimum (perennial sea ice). It is very likely that the annual mean Antarctic sea ice extent increased at a rate in the range of 1.2 to 1.8% per decade between 1979 and 2012. There are strong regional differences in the Antarctic annual rate, with extent increasing in some regions and decreasing in others.
  • The IPCC reports with high confidence that the rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia. Over the period 1901–2010, global mean sea level rose by 0.19 m.  Since the early 1970s, glacier mass loss and ocean thermal expansion from warming together explain about 75% of the observed global mean sea level rise.
  • Averaged over the mid-latitude land areas of the Northern Hemisphere, precipitation has increased since 1901. There are likely more land regions where the number of heavy precipitation events has increased than where it has decreased. The frequency or intensity of heavy precipitation events has likely increased in North America and Europe.
  • It is very likely that regions of high salinity where evaporation dominates have become more saline, while regions of low salinity where precipitation dominates have become fresher since the 1950s. These regional trends in ocean salinity provide indirect evidence that evaporation and precipitation over the oceans have changed.
  • It is very likely that the number of cold days and nights has decreased and the number of warm days and nights has increased on the global scale. It is likely that the frequency of heat waves has increased in large parts of Europe, Asia and Australia.
  • The globally averaged combined land and ocean surface temperature data show a warming of 0.85°C, over the period 1880–2012.
  • On a global scale, the ocean warming is largest near the surface, and the upper 75 m warmed by 0.11 [0.09 to 0.13] °C per decade over the period 1971–2010.  More than 60% of the net energy increase in the climate system is stored in the upper ocean.

According to the IPCC, where are we going with climate change in the next several decades? There is no crystal ball, but the report addresses likely emission rates and their predicted effects on global temperatures under a range of modeled scenarios depending on how aggressive the world does, or does not get on curbing emissions. Their predictions include:

  • Global surface temperature change for the end of the 21st century is likely to exceed 1.5°C relative to 1850 to 1900 for most modeled scenarios.
  • It is likely to exceed 2°C for the scenarios in which we do less to curb emissions.
  • Warming will continue beyond 2100 under nearly all modeled scenarios. Warming will continue to exhibit interannual-to-decadal variability and will not be regionally uniform.
  • Global mean sea level will continue to rise during the 21st century; the rate of sea level rise will very likely exceed that observed during 1971–2010 due to increased ocean warming and increased loss of mass from glaciers and ice sheets.

So in sum, where are we heading? If we don’t seize our vanishing window of opportunity to curb carbon emissions quickly and profoundly, we’re heading into a warmer, more acidic, and more climatologically extreme world.

This is not to say that there are not aspects of climate change that have not occurred before in the earth’s history, and this is where climate skeptics often like to hang their hat. Interglacial periods, including those within human history of a few hundred thousand years ago, may have seen warmer global temperatures, and higher sea levels, than we see now and are predicting as likely over the next several decades. As the IPCC report states, “There is very high confidence that maximum global mean sea level during the last interglacial period (129,000 to 116,000 years ago) was, for several thousand years, at least 5 m higher than present and high confidence that it did not exceed 10 m above present. During the last interglacial period, the Greenland ice sheet very likely contributed between 1.4 and 4.3 m to the higher global mean sea level, implying an additional contribution from the Antarctic ice sheet.” However, New York, Shanghai and Mumbai, with their millions of inhabitants, and the other half billion people living close to our coastlines around the world, weren’t around the last time sea levels were 5m above their current levels.  Nor were there hundreds of millions of us relying on a food chain that is at its foundation based on calcified organisms threatened by acidification. Nor were millions of houses built in the paths of greater storm activity that may well have accompanied past warmer climates. If we know that humans are substantially influencing climate change and attendant sea level rise and ocean acidification, the argument that “its happened before”, is not that useful or relevant, if its within our power to mitigate a substantial source of that change.

So that is where we are in the state of the climate, update 5. My Action title is a bit facetious, I wasn’t weeping, but I was, as I always am in reading about the rate and extent of change we are creating, deeply and profoundly concerned, as we should all be, about where our current path is taking us in terms of reshaping the world we know and the ecological systems we have evolved with. Its enough to make you want to do something, right? I hope so.

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