James Hansen, et al. Young People’s Burden: Requirement of Negative CO2 Emissions. Earth System Dynamic doi:10.5194/esd-2016-42
Abstract. The rapid rise of global temperature that began about 1975 continues at a mean rate of about 0.18 °C/decade, with the current annual temperature exceeding +1.25 °C relative to 1880–1920. Global temperature has just reached a level similar to the mean level in the prior interglacial (Eemian) period, when sea level was several meters higher than today, and, if it long remains at this level, slow amplifying feedbacks will lead to greater climate change and consequences.
The growth rate of climate forcing due to human-caused greenhouse gases (GHGs) increased over 20 % in the past decade mainly due to resurging growth of atmospheric CH4, thus making it increasingly difficult to achieve targets such as limiting global warming to 1.5 °C or reducing atmospheric CO2 below 350 ppm.
Such targets now require “negative emissions”, i.e., extraction of CO2 from the atmosphere. If rapid phasedown of fossil fuel emissions begins soon, most of the necessary CO2 extraction can take place via improved agricultural and forestry practices, including reforestation and steps to improve soil fertility and increase its carbon content. In this case, the magnitude and duration of global temperature excursion above the natural range of the current interglacial (Holocene) could be limited and irreversible climate impacts could be minimized.
In contrast, continued high fossil fuel emissions by the current generation would place a burden on young people to undertake massive technological CO2 extraction, if they are to limit climate change. Proposed methods of extraction such as bioenergy with carbon capture and storage (BECCS) or air capture of CO2 imply minimal estimated costs of 104–570 trillion dollars this century, with large risks and uncertain feasibility.
Continued high fossil fuel emissions unarguably sentences young people to either a massive, possibly implausible cleanup or growing deleterious climate impacts or both, scenarios that should provide both incentive and obligation for governments to alter energy policies without further delay.
Humans will have to not only stop emitting greenhouse gases by 2085, but also develop technology that will result in negative emissions — the removal of 15 billion tons of carbon dioxide from the atmosphere each year by the end of the century — in order to prevent global warming from exceeding 2°C (3.6°F), according to a new study.
Human greenhouse gas emissions, including methane and carbon dioxide, have already warmed the globe more than 1°C (1.8°F) compared to pre-industrial levels. The Paris Climate Agreement negotiated last year seeks to cap warming to below 2°C, while at the same time pursuing an even more ambitious goal of limiting warming to 1.5°C.
But according to a new National Center for Atmospheric Research study, just cutting emissions under the Paris agreement may not be enough to keep global warming from blasting past 2°C, said Benjamin Sanderson, the study’s lead author.
Meeting the Paris agreement as written will require a long-term commitment to negative emissions in the last two decades of the century, he said…
Sanderson et al. What would it take to achieve the Paris temperature targets? Geophysical Research Letters Full publication history DOI: 10.1002/2016GL069563
About 45 minutes into my flight home from Dublin in July, I glanced out the window to see a freeway of enormous icebergs floating in the ocean. A few minutes later we reached the southeast coast of Greenland. Dark craggy peaks pierced the sky with giant rivers of murky snowmelt pouring out to the sea, like diseased veins of a severely ill patient.
No longer a sheet of white snow and ice stretching to its pelagic edge, Greenland is now the poster child for climate change and humanity’s growing impacts on our biosphere.
Fortunately there is hope. A “perfect storm” of new laws and statutes on nature-based solutions – globally, nationally and regionally- presents opportunities for Point Blue and our partners to develop and assess natural infrastructure demonstration projects that provide multiple benefits to society and wildlife.
The historic Paris climate accord, signed by every nation in the world, officially went into effect in early November. It includes a global commitment to sustaining healthy ecosystems to help sequester greenhouse gas (GHG) pollution and reduce the impacts of increasing extremes such as drought, heatwaves, storms and sea level rise.
Two new California laws require state agencies, counties and cities to incorporate natural infrastructure into their climate adaptation efforts. Another pioneering California law allows for payments for ecosystem services, recognizing source watersheds (including meadows, streams and upland habitat) as water infrastructure and opening the door to public works dollars for habitat restoration.
And, Senate Bill 32, signed into law by Governor Brown in September, extends California’s climate law by requiring a reduction in GHGs to 40% below 1990 levels by 2030. This means reducing the state’s emissions by ~ 100 million metric tons per year more than current policies get us to.
Nature-based solutions will be essential to achieving this urgent outcome for people and wildlife.
Posted on 15 August 2016 by dana1981 skepticalscience.com
While most people accept the reality of human-caused global warming, we tend not to view it as an urgent issue or high priority. That lack of immediate concern may in part stem from a lack of understanding that today’s pollution will heat the planet for centuries to come, as explained in this Denial101x lecture.
So far humans have caused about 1°C warming of global surface temperatures, but if we were to freeze the level of atmospheric carbon dioxide at today’s levels, the planet would continue warming. Over the coming decades, we’d see about another 0.5°C warming, largely due to what’s called the “thermal inertia” of the oceans (think of the long amount of time it takes to boil a kettle of water). The Earth’s surface would keep warming about another 1.5°C over the ensuing centuries as ice continued to melt, decreasing the planet’s reflectivity.
To put this in context, the international community agreed in last year’s Paris climate accords that we should limit climate change risks by keeping global warming below 2°C, and preferably closer to 1.5°C. Yet from the carbon pollution we’ve already put into the atmosphere, we’re committed to 1.5–3°C warming over the coming decades and centuries, and we continue to pump out over 30 billion tons of carbon dioxide every year.
The importance of reaching zero or negative emissions
We can solve this problem if, rather than holding the amount of atmospheric carbon dioxide steady, it falls over time. As discussed in the above video, Earth naturally absorbs more carbon than it releases, so if we reduce human emissions to zero, the level of atmospheric carbon dioxide will slowly decline. Humans can also help the process by finding ways to pull carbon out of the atmosphere and sequester it.
Scientists are researching various technologies to accomplish this, but we’ve already put over 500 billion tons of carbon dioxide into the atmosphere. Pulling a significant amount of that carbon out of the atmosphere and storing it safely will be a tremendous challenge, and we won’t be able to reduce the amount in the atmosphere until we first get our emissions close to zero.
There are an infinite number of potential carbon emissions pathways, but the 2014 IPCC report considered four possible paths that they called RCPs. In one of these (called RCP 2.6 or RCP3-PD), we take immediate, aggressive, global action to cut carbon pollution, atmospheric carbon dioxide levels peak at 443 ppm in 2050, and by 2100 they’ve fallen back down to today’s level of 400 ppm. In two others (RCPs 4.5 and 6.0) we act more slowly, and atmospheric levels don’t peak until the year 2150, then they remain steady, and in the last (RCP8.5) carbon dioxide levels keep rising until 2250.
As the figure below shows [see here], in the first scenario, global warming peaks at 2°C and then temperatures start to fall toward the 1.5°C level, meeting our Paris climate targets. In the other scenarios, temperatures keep rising centuries into the future.
This is the critical decade
We don’t know what technologies will be available in the future, but we do know that the more carbon pollution we pump into the atmosphere today, the longer it will take and more difficult it will be to reach zero emissions and stabilize the climate. We’ll also have to pull that much more carbon out of the atmosphere.
It’s possible that as in three of the IPCC scenarios, we’ll never get all the way down to zero or negative carbon emissions, in which case today’s pollution will keep heating the planet for centuries to come. Today’s carbon pollution will leave a legacy of climate change consequences that future generations may struggle with for the next thousand years.