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The Keeling curve shows atmospheric CO2 measured at Mauna Loa in Hawaii from 1958 to 2013, rising from 315 to 395 ppm CO2, and showing the cycle in spring and fall when trees grow and then shed their leaves. The rate of increase, shown later in this presentation, has climbed from 1 ppm per year to 1.5 and now slightly over 2 ppm CO2 per year. At that rate, we will exceed 450 ppm CO2 by 2035, if not sooner.
The rate of increase, shown later in this presentation, has climbed from 1 ppm per year to 1.5 and now slightly over 2 ppm CO2 per year. At that rate, we will exceed 450 ppm CO2 by 2035, if not sooner. This is a key metric, as it sets a time window in which we have to act, as once 450 ppm CO2 is reached, it is unlikely that disastrous if not catastrophic consequences of climate change will be felt worldwide.
Estimates of future emissions are called ‘trajectories’ and in this slide represent three scenarios. One is a low emission strategy where we start a rapid reduction in carbon intensity beginning in 2020, and the ocean, atmosphere, and land begin to absorb carbon emissions, and atmospheric CO2 eventually stabilizes at ~400 ppm. In percentage terms, this has the highest probability of climate stabilization, but the least probability of actually happening. In the second scenario, carbon emissions also begin to decline in 2020, but not as fast, and the atmosphere rises in CO2 and then declines to ~ 450 ppm CO2. This has a 50% probability of success, but is probably not very likely, as most emission modeling shows an increase in energy intensity to ~2040 or later, and no decrease in carbon intensity until ~ 2035. As such, emissions rise as high as 500 ppm CO2, before stabilizing. This would be a climate disaster, but considering our nearly ineffectual governance, probably the most likely to occur.
While many people, including politicians and leaders, would wait until it was so painfully obvious that climate change was both real and a significant impact, we simply don’t have 20 years to ‘wait and see’. We have already seen significant impacts, (heat storms, drought, fires, and superstorms), at less than one degree Celsius of warming, and have been led to believe that 2 degrees is the edge of stability. On the contrary, other scientists have suggested that 450 ppm atmospheric CO2 is the threshold we should not cross, for both climate and ocean acidity (pH 8 and undersaturation of bicarbonate ion). Here are the facts:
We are headed right at 450 ppm CO2, currently at ~400 ppm CO2, and rising at a little over 2 ppm CO2 per year (a rate that is also increasing), and will reach that level by 2035, if not sooner. There are two problems with 450 ppm CO2. First, the level of ‘committed warming’ will be ~ 2 degrees Celsius. Committed warming means the temperature of the ocean will eventually (~50 years) rise to that level. Second, as CO2 dissolves in the ocean (25% or more will end up there) the pH of the ocean decreases (from 8.15 to ~ 8.0) leading to undersaturation of bicarbonate ion, causing coral to dissolve (90% will be lost), and severely impacting plankton ability to form shells. Plankton are the base of the food chain. There is a possibility that amplifying feedbacks (albedo and methane hydrate destabilization) could cause us to warm even further, to 3 deg Celsius. Energy investments in infrastructure typically have a 25 to 40 year lifetime (physical and economic depreciation), so investments in carbon intensive infrastructure today will last at least to at least 2035 and possibly to 2040. Decisions we make today (and in the first decade of the 21st Century) will likely take us well over 450 ppm CO2, and some fear as much as 500 ppm CO2.
For a number of years since 2009 and especially 2011-2013, the US has experienced both severe drought and heats storms, that combined with high humidity (heat index) have caused extensive suffering.
While it was a Category 2 storm off the coast of the Northeastern United States, the storm became the largest Atlantic hurricane on record (as measured by diameter, with winds spanning 1,100 miles (1,800 km)). Estimates as of June 2013 assess damage to have been over $68 billion (2013 USD), a total surpassed only by Hurricane Katrina. At least 286 people were killed along the path of the storm in seven countries (Wikipedia http://en.wikipedia.org/wiki/Hurricane_Sandy)
Ocean acidification is one of two wild cards, the other being methane hydrates, that could spell real trouble for human civilization. As CO2 is added to the atmosphere, about 25% also dissolves in the ocean, leading to production of bicarbonate ion, a natural process, but too much adds extra protons, which remove CO2 from solution (undersaturation). The consumption of carbonate ions impedes calcification. CO2 + H2O =&gt; H2CO3 which becomes HCO3- + H+ (a weak acid) when too much CO2 dissolves, the added proton will seek out unprotonated CO32- bicarbonate ion. As atmospheric CO2 reaches 450 ppm, pH drops to ~8, and the concentration of CO2 exceeds bicarbonate ion, leading to undersaturation of the anion. That in turns will not only slow calcification, but can lead to dissolution of corals, and significant drop in phytoplankton, which may have already begun (Climos and Planktos) in the 20th Century. Losing the bottom of the food chain and a carbon dioxide pump in itself could lead to problems in both ocean productivity as well as future ability of the oceans to soak up CO2.
When CO2 dissolves in seawater, carbonic acid is produced via the reaction: CO2 + H2O =&gt; H2CO3 This carbonic acid dissociates in the water, releasing hydrogen ions and bicarbonate: H2CO3 =&gt; H+ + HCO3 The increase in the hydrogen ion concentration causes an increase in acidity, since acidity is defined by the pH scale, where pH = -log [H+] (so as hydrogen increases, the pH decreases). This log scale means that for every unit decrease on the pH scale, the hydrogen ion concentration has increased 10-fold. One result of the release of hydrogen ions is that they combine with any carbonate ions in the water to form bicarbonate: H+ + CO32- &lt;=&gt; HCO3- This removes carbonate ions from the water, making it more difficult for organisms to form the CaCO3 they need for their shells.
Arctic Sea Ice is diminishing at an accelerating rate, and the arctic may be ‘ice free’ in summer as early as 2015. This will have profound affects to albedo, adding energy to the arctic sea, destabilizing methane hydrates, and further adding to instability and/or erratic behavior of the jet stream and ocean currents. PIOMAS utilizes satellite tools for remote imaging of planet earth.
Methane hydrates are a wild card in the climate system, as they contain thousands of gigatons of methane complexed with water in frozen slurry, and only stable at very high pressure, and very cold temperatures. The stability of methane hydrates, called the hydrate stability zone, requires very cold temperatures, and great depths (thousands of feet). As shown in the chart, the Eastern Siberian Ice Shelf (ESAS) is especially prone to methane release as hydrates on the sea floor are in relatively shallow waters (hundreds of meters deep or less) with less than one or two degrees Celsius of margin between stability and release of methane. Recent studies (Natalia Shakova) of the Arctic Research Center have shown a doubling of methane release since 2009, from 8 teragrams (mega tons) to 17 teragrams. This translates to 6 ppb methane release, significant to see in the atmosphere. Scientists at the arctic research center are concerned about two scenarios, one where a sudden release of methane occurs that can temporarily ‘swamp’ hydroxyl ion, leading to a longer half-life and consequently a much higher GWP (Green House Warming Potential), and second, a sustained release of up to 50 gigatons (3.4% of the estimated 1400 gigatons stored under permafrost in the ESAS) which when multiplied by the GWP of (at least 20) is equal to 1,000 gigatons of carbon, what Hansen and others have calculated to be the total carbon budget to keep us under 2 degrees Celsius.
This presentation uses a Creative Commons copyright. This PowerPoint presentation was prepared for use by academic professionals, faculty and students to better understand and communicate climate change. It may be used as is, or remixed. Please use the references for images and other texts, and do not assume images are used with permission. If you wish to contact me, I can be reached at [email_address].
Understanding earth’s greenhouse
Robert D. Cormia
Overview and Goals
• What keeps earth warm?
• How does the Greenhouse work?
• What does Vostok tell us?
• Fossil fuel emissions and GHGs
• Current and future forcing, feedbacks
• What you can do be being smarter
Black Body Radiation
The Greenhouse Effect
An overview of the Greenhouse Effect. From IPPC Working Group 1 contribution, Science of Climate Change, Second Assessment Report 1996
Greenhouse Gasses (GHGs)
Methane – CH4
Carbon dioxide – CO2
CO2 is the Greenhouse Gas that we follow the most as fossil fuels
contribute to it directly. CO2 also absorbs energy near 700 nm. A doubling
of CO2 would raise earth’s temperature by nearly 3 degrees Celsius.
• Potent GHG –
20x CO2 / mole
• 10 year half-life
• -OH combination
• Agriculture plus
• Sleeping giant
• Water vapor is
actually the most
potent GHG (by
• Reacts to changes in
• Key in feedbacks
Vostok Ice Core Data
•A perfect correlation between CO2, temperature, and sea level
•For every one ppm CO2, sea level rises 1 meter, temp rises .05 C (global)
•Process takes 100 years to add 1 ppm CO2, and reach thermal equilibrium
This is not just a correlation, this is a complex and dynamic process, with multiple
inputs. Touching one input affects all other inputs, and increases in temperature
becomes a further feedback and multiplier of these inputs.
GHGs and Vostok Data
James Kirchner Department of Earth and Planetary Science, University of California, Berkeley
Carbon Emissions and CO2
• Carbon burned => CO2
• Linear from 1850 to 2000
- ppm CO2 =2.55 e10-4 *M tons C +
• ~ 50% of carbon goes
into atmospheric CO2
– 50% oceans / soil
• Trend is constant over
100 years – is this how
the biosphere will react
over the next 500 years?
Year C burned ppm CO2
1900 12307 295
1910 19174 300
1920 28050 305
1930 37914 310
1940 48566 310
1950 62324 315
1960 83453 320
1970 115935 325
1980 164083 340
1990 219365 350
2000 283373 370
2010 365000 390
• We are adding 2+ ppm CO2 to the
atmosphere every year, and is increasing
• China passed US in GHGs emissions 5
years ago, and is now nearly double US
• Oil and hydrocarbons are actually plentiful
• Coal is still setting production records
• Population, wealth, and consumption
CO2 Trajectories to 2oC
Don’t have 20 years to Wait
• Trajectory to 450 ppm CO2 (2032-2035)
– 450 ppm CO2 => 2 deg C committed/forcing
– Amplifying feedbacks take us to 3+ deg C
• Ocean acidity 450 ppm CO2 => pH 8
– concentration [CO2] = [HCO3]
• Decisions made today impact 2035
– Still investing in carbon intensive energy
– At 2+ ppm/year, for 20+ years, 450 ppm CO2
Heat Storms in the US
Record heat across the US in summer, including an oppressive heat index
CO2 dissolves in water to produce mild carbonic acid, which dissociates into bicarbonate and
carbonate ion. Increasing acidity removes carbonate ion from solution. At pH 8 (450 ppm CO2)
carbonate ion is under-saturated, shells will be difficult to form and stay stable.
Arctic Sea Open Ice in 2015
What you can do…
• Understand earth’s greenhouse process
• Decide if you want to make a difference
• Measure your carbon footprint!
• Develop your own climate action plan
• Talk to people about what you know
• Science isn’t holding us back
• Our collective behaviors are
• Technology isn’t (all) the answer
• Efficiency and energy intensity
• Making better carbon decisions
• Climate Change Index -
• EIA – http://www.eia.gov
• NOAA Climate Center
• Skeptical Science - https://www.skepticalscience.com/
• International Arctic Research Center
This presentation is intended solely for use/remix for educational purposes