Climate change update

Additions to Guy 

McPherson's Climate Change 

Update

Yesterday Guy McPherson made additions to his Climate Change Update essay.

These were summarised in the latest broadcast of Nature Bats Last.

I have extracted Guy's latest additions and summarised them here with links to the original scientific papers. Guy's comments from his essay are in large italics.

A paper in the 3 February 2016 issue of Nature finds a long-sought “smoking gun” with respect to carbon storage in the deep ocean. As it turns outs, carbon was stored in the depths of the Southern Ocean when atmospheric carbon dioxide levels were quite low

Covariation of deep Southern Ocean oxygenation and atmospheric CO₂ through the last ice age

No single mechanism can account for the full amplitude of past atmospheric carbon dioxide (CO2) concentration variability over glacial–interglacial cycles1. A build-up of carbon in the deep ocean has been shown to have occurred during the Last Glacial Maximum2, 3. However, the mechanisms responsible for the release of the deeply sequestered carbon to the atmosphere at deglaciation, and the relative importance of deep ocean sequestration in regulating millennial-timescale variations in atmospheric CO2 concentration before the Last Glacial Maximum, have remained unclear. Here we present sedimentary redox-sensitive trace-metal records from the Antarctic Zone of the Southern Ocean that provide a reconstruction of transient changes in deep ocean oxygenation and, by inference, respired carbon storage throughout the last glacial cycle. Our data suggest that respired carbon was removed from the abyssal Southern Ocean during the Northern Hemisphere cold phases of the deglaciation, when atmospheric CO2 concentration increased rapidly, reflecting—at least in part—a combination of dwindling iron fertilization by dust and enhanced deep ocean ventilation. Furthermore, our records show that the observed covariation between atmospheric CO2 concentration and abyssal Southern Ocean oxygenation was maintained throughout most of the past 80,000 years. This suggests that on millennial timescales deep ocean circulation and iron fertilization in the Southern Ocean played a consistent role in modifying atmospheric CO2 concentration

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Afforestation and forest management are considered to be key instruments in mitigating climate change. But, as indicated by a paper in the 5 February 2016 issue of Science, the expansion of Europe’s forests toward dark green conifers has stoked global warming. The darkly colored evergreen have been planted for their ability to grow quickly with relatively little management, but their propensity to sequester atmospheric carbon dioxide has been outstripped by their dark color. Thus, according to the abstract of the paper, “two and a half centuries of forest management in Europe have not cooled the climate.” 

Europe’s forest management did not mitigate climate warming

"For most of the past 250 years, surprisingly it seems that Europe's managed forests have been a net source of carbon, contributing to climate warming rather than mitigating it. Naudts et al. reconstructed the history of forest management in Europe in the context of a land-atmosphere model. The release of carbon otherwise stored in litter, dead wood, and soil carbon pools in managed forests was one key factor contributing to climate warming. Second, the conversion of broadleaved forests to coniferous forests has changed the albedo and evapotranspiration of those forests, also leading to warming. Thus, climate change mitigation policies in Europe and elsewhere may need to consider changes in forest management.

Science, this issue p. 59

As pointed out by the Bulletin of the Atomic Scientists on 18 February 2016, climate change isaccelerating, not slowing, with the construction and use of nuclear power facilities. James Hansen take note. 

Climate protection through nuclear power plants? Hardly.

The electrical power production sector accounts for about 28 percent of global anthropogenic carbon dioxide emissions and constitutes by far the largest source of greenhouse gas emissions. That is why supposedly carbon dioxide-free nuclear power plants have frequently been praised as a panacea for addressing climate change. However, in 2013 nuclear electricity contributed just 10.6 percent of global electricity generation, and because electricity represents only 18 percent of total global final energy consumption, the nuclear share is just 1.7 percent of global final energy consumption. Even if generation in nuclear power plants could be increased significantly, nuclear power will remain a marginal energy source. Therefore, the turnaround in energy systems has to prioritize energy efficiency and the use of renewable energy technologies and cogeneration plants, which do not cause any more carbon dioxide emissions than nuclear power plants.

From a systemic perspective, nuclear power plants are by no means free of carbon dioxide emissions. Today, they produce up to one third of the greenhouse gases that large modern gas power plants produce. Carbon dioxide emissions connected to production of nuclear energy amounts to (depending on where the uranium used in a reactor is mined and enriched) between 7 and 126 grams of carbon dioxide equivalent per kilowatt hour, according to an analysis by International Institute for Sustainability Analysis and Strategy co-founder Uwe Fritsche. For a typical nuclear power plant in Germany, the specific emission estimate of 28 grams has been calculated. An initial estimate of global carbon dioxide emissions through the generation of nuclear electricity in 2014 registered at about 110,000,000 tons of carbon dioxide equivalent—or roughly as much as the carbon dioxide emissions of a country like the Czech Republic. And this data does not even include the emissions caused by storage of nuclear waste.

In the coming decades, indirect carbon dioxide emissions from nuclear power plants will increase considerably, because high-grade resources of uranium are exhausted and much more fossil energy will have to be used to mine uranium. In view of this trend, nuclear power plants will no longer have an emissions advantage over modern gas-fired power plants, let alone in comparison to the advantages offered by increased energy efficiency or greater use of renewable energies.

Nuclear power plants may also contribute to climate change by emitting radioactive isotopes such as tritium or carbon 14 and the radioactive noble gas krypton 85. Krypton 85 is produced in nuclear power plants and released on a massive scale in the reprocessing of spent fuel. The concentration of krypton 85 in Earth's atmosphere has soared over the last few years as a result of nuclear fission, reaching a new record. Krypton 85 increases the natural, radiation-induced ionization of the air. Thus the electrical balance of the Earth's atmosphere changes, which poses a significant threat to weather patterns and climate. Even though krypton 85 is “one of the most toxic agents for climate,” according to German physicist and political figure Klaus Buchner, these emissions have not received any attention in international climate-protection negotiations down to the present.

As for the assertion that nuclear power is needed to promote climate protection, exactly the opposite would appear to be the case: Nuclear power plants must be closed down quickly to exert pressure on operators and the power plant industry to redouble efforts at innovation in the development of sustainable and socially compatible energy technologies and especially the use of smart energy services

A paper in the 8 February 2016 online issue of Nature Climate Change points outthe long-term impacts of ongoing changes in Earth’s climate: “Here, we argue that the twentieth and twenty-first centuries … need to be placed into a long-term context that includes the … next ten millennnia, over which time the projected impacts of anthropogenic climate change will grow and persist. This long-term perspective illustrates that policy decisions made in the next few years to decades will have profound impacts on global climate, ecosystems and human societies — not just for this century, but for the next ten millenia and beyond.” **

Consequencesof twenty-first-century policy for multi-millennial climate and  sea-level change 

Most of the policy debate surrounding the actions needed to mitigate and adapt to anthropogenic climate change has been framed by observations of the past 150 years as well as climate and sea-level projections for the twenty-first century. The focus on this 250-year window, however, obscures some of the most profound problems associated with climate change. Here, we argue that the twentieth and twenty-first centuries, a period during which the overwhelming majority of human-caused carbon emissions are likely to occur, need to be placed into a long-term context that includes the past 20 millennia, when the last Ice Age ended and human civilization developed, and the next ten millennia, over which time the projected impacts of anthropogenic climate change will grow and persist. This long-term perspective illustrates that policy decisions made in the next few years to decades will have profound impacts on global climate, ecosystems and human societies — not just for this century, but for the next ten millennia and beyond

An abstract of a paper to be published in the April 2016 issue of Biogeochemistryincludes these sentences: “Rising temperatures and nitrogen (N) deposition, both aspects of global environmental change, are proposed to alter soil organic matter (SOM) biogeochemistry. … Overall, this study shows that the decomposition and accumulation of molecularly distinct SOM components occurs with soil warming and N amendment and may subsequently alter soil biogeochemical cycling.” In other words, as global temperatures rise, the organic matter in forests appears to break down more quickly, thereby accelerating the release of carbon into the atmosphere. **

Increasing drought threatens almost all forests in the United States, according to apaper in the 21 February 2016 online issue of Global Change Biology

. According to the paper’s abstract, “diebacks, changes in composition and structure, and shifting range limits are widely observed.” 

The impacts of increasing drought on forest dynamics, structure, and biodiversity in the United States

“We synthesize insights from current understanding of drought impacts at stand-to-biogeographic scales, including management options, and we identify challenges to be addressed with new research. Large stand-level shifts underway in western forests already are showing the importance of interactions involving drought, insects, and fire. Diebacks, changes in composition and structure, and shifting range limits are widely observed. In the eastern US, the effects of increasing drought are becoming better understood at the level of individual trees, but this knowledge cannot yet be confidently translated to predictions of changing structure and diversity of forest stands. While eastern forests have not experienced the types of changes seen in western forests in recent decades, they too are vulnerable to drought and could experience significant changes with increased severity, frequency, or duration in drought. Throughout the continental United States, the combination of projected large climate-induced shifts in suitable habitat from modeling studies and limited potential for the rapid migration of tree populations suggests that changing tree and forest biogeography could substantially lag habitat shifts already underway. Forest management practices can partially ameliorate drought impacts through reductions in stand density, selection of drought-tolerant species and genotypes, artificial regeneration, and the development of multistructured stands. However, silvicultural treatments also could exacerbate drought impacts unless implemented with careful attention to site and stand characteristics. Gaps in our understanding should motivate new research on the effects of interactions involving climate and other species at the stand scale and how interactions and multiple responses are represented in models. This assessment indicates that, without a stronger empirical basis for drought impacts at the stand scale, more complex models may provide limited guidance.”

** Over the past 10 years, the Atlantic Ocean has soaked up 50 percent more carbon dioxide than it did the decade before, measurably speeding up the acidification of the ocean, according to a paper published in the 30 January 2016 issue of Global Biogeochemical Cycles. **

Rapid anthropogenic changes in CO₂ and pH in the Atlantic Ocean: 2003–2014

"The extended multilinear regression method is used to determine the uptake and storage of anthropogenic carbon in the Atlantic Ocean based on repeat occupations of four cruises from 1989 to 2014 (A16, A20, A22, and A10), with an emphasis on the 2003–2014 period. The results show a significant increase in basin-wide anthropogenic carbon storage in the North Atlantic, which absorbed 4.4 ± 0.9 Pg C decade−1 from 2003 to 2014 compared to 1.9 ± 0.4 Pg C decade−1 for the 1989–2003 period. This decadal variability is attributed to changing ventilation patterns associated with the North Atlantic Oscillation and increasing release of anthropogenic carbon into the atmosphere. There are small changes in the uptake rate of CO2 in the South Atlantic for these time periods (3.7 ± 0.8 Pg C decade−1 versus 3.2 ± 0.7 Pg C decade−1). Several eddies are identified containing ~20% more anthropogenic carbon than the surrounding waters in the South Atlantic demonstrating the importance of eddies in transporting anthropogenic carbon. The uptake of carbon results in a decrease in pH of ~0.0021 ± 0.0007 year−1 for surface waters during the last 10 years, in line with the atmospheric increase in CO2."

For the first time, researchers have documented algae-related toxins in Arctic sea mammals. Specifically, toxins produced by harmful algal blooms are showing up in Alaska marine mammals as far north as the Arctic Ocean — much farther north than ever reported previously, according to a paper in the 11 February 2016 issue ofHarmful Algae. 

The abstract indicates, “In this study, 905 marine mammals from 13 species were sampled including; humpback whales, bowhead whales, beluga whales, harbor porpoises, northern fur seals, Steller sea lions, harbor seals, ringed seals, bearded seals, spotted seals, ribbon seals, Pacific walruses, and northern sea otters. Domoic acid was detected in all 13 species examined and had the greatest prevalence in bowhead whales (68%) and harbor seals (67%). Saxitoxin was detected in 10 of the 13 species … These results provide evidence that … toxins are present throughout Alaska waters at levels high enough to be detected in marine mammals and have the potential to impact marine mammal health in the Arctic marine environment.” 

Prevalence of algal toxins in Alaskan marine mammals foraging in a changing arctic and subarctic environment

Current climate trends resulting in rapid declines in sea ice and increasing water temperatures are likely to expand the northern geographic range and duration of favorable conditions for harmful algal blooms (HABs), making algal toxins a growing concern in Alaskan marine food webs. Two of the most common HAB toxins along the west coast of North America are the neurotoxins domoic acid (DA) and saxitoxin (STX). Over the last 20 years, DA toxicosis has caused significant illness and mortality in marine mammals along the west coast of the USA, but has not been reported to impact marine mammals foraging in Alaskan waters. Saxitoxin, the most potent of the paralytic shellfish poisoning toxins, has been well-documented in shellfish in the Aleutians and Gulf of Alaska for decades and associated with human illnesses and deaths due to consumption of toxic clams. There is little information regarding exposure of Alaskan marine mammals. Here, the spatial patterns and prevalence of DA and STX exposure in Alaskan marine mammals are documented in order to assess health risks to northern populations including those species that are important to the nutritional, cultural, and economic well-being of Alaskan coastal communities. In this study, 905 marine mammals from 13 species were sampled including; humpback whales, bowhead whales, beluga whales, harbor porpoises, northern fur seals, Steller sea lions, harbor seals, ringed seals, bearded seals, spotted seals, ribbon seals, Pacific walruses, and northern sea otters. Domoic acid was detected in all 13 species examined and had the greatest prevalence in bowhead whales (68%) and harbor seals (67%). Saxitoxin was detected in 10 of the 13 species, with the highest prevalence in humpback whales (50%) and bowhead whales (32%). Pacific walruses contained the highest concentrations of both STX and DA, with DA concentrations similar to those detected in California sea lions exhibiting clinical signs of DA toxicosis (seizures) off the coast of Central California, USA. Forty-six individual marine mammals contained detectable concentrations of both toxins emphasizing the potential for combined exposure risks. Additionally, fetuses from a beluga whale, a harbor porpoise and a Steller sea lion contained detectable concentrations of DA documenting maternal toxin transfer in these species. These results provide evidence that HAB toxins are present throughout Alaska waters at levels high enough to be detected in marine mammals and have the potential to impact marine mammal health in the Arctic marine environment.

According to a paper in the 18 December 2015 issue of Science Advances, “Many large tropical trees with sizeable contributions to carbon stock rely on large vertebrates for seed dispersal and regeneration, however many of these frugivores are threatened by hunting, illegal trade, and habitat loss. … we found that defaunation has the potential to significantly erode carbon storage even when only a small proportion of large-seeded trees are extirpated.” In other words, climate change that causes loss of habitat for animals reduces the ability of tropical forests to store carbon, thus creating a self-reinforcing feedback loop.

Defaunation affects carbon storage in tropical forests

"Carbon storage is widely acknowledged as one of the most valuable forest ecosystem services. Deforestation, logging, fragmentation, fire, and climate change have significant effects on tropical carbon stocks; however, an elusive and yet undetected decrease in carbon storage may be due to defaunation of large seed dispersers. Many large tropical trees with sizeable contributions to carbon stock rely on large vertebrates for seed dispersal and regeneration, however many of these frugivores are threatened by hunting, illegal trade, and habitat loss. We used a large data set on tree species composition and abundance, seed, fruit, and carbon-related traits, and plant-animal interactions to estimate the loss of carbon storage capacity of tropical forests in defaunated scenarios. By simulating the local extinction of trees that depend on large frugivores in 31 Atlantic Forest communities, we found that defaunation has the potential to significantly erode carbon storage even when only a small proportion of large-seeded trees are extirpated. Although intergovernmental policies to reduce carbon emissions and reforestation programs have been mostly focused on deforestation, our results demonstrate that defaunation, and the loss of key ecological interactions, also poses a serious risk for the maintenance of tropical forest carbon storage."

From the 22 December 2015 online issue of the Proceedings of the National Academy of Sciences comes a paper pointing out the link between Arctic sea ice and regional precipitation

The abstract of the paper includes the following lines: “Global climate is influenced by the Arctic hydrologic cycle, which is, in part, regulated by sea ice through its control on evaporation and precipitation. … We find that the independent, direct effect of sea ice on the increase of the percentage of Arctic sourced moisture … likely result in increases of precipitation and changes in energy balance, creating significant uncertainty for climate predictions.” In other words, to quote the lead author of the paper, “If you remove sea ice from an Arctic area, you open up the ocean to the atmosphere, and evaporate more water, which forms precipitation.”

Influence of sea ice on Arctic precipitation

Significance

There has been a growing consensus that a decrease in sea ice would cause an increase in Arctic precipitation because of the potential for increased local evaporation. We quantify the effect of sea ice on the percentage of moisture sourced from the Arctic, using measurements of the isotopic composition of precipitation at six sites across the Arctic. These moisture proportion changes are important in that they indicate systematic adjustment and/or reorganization of the global hydrological cycle with climate change and provide validation for climate models. We explore how much these changes may increase Arctic precipitation and its impact on the energy balance.

Abstract

Global climate is influenced by the Arctic hydrologic cycle, which is, in part, regulated by sea ice through its control on evaporation and precipitation. However, the quantitative link between precipitation and sea ice extent is poorly constrained. Here we present observational evidence for the response of precipitation to sea ice reduction and assess the sensitivity of the response. Changes in the proportion of moisture sourced from the Arctic with sea ice change in the Canadian Arctic and Greenland Sea regions over the past two decades are inferred from annually averaged deuterium excess (d-excess) measurements from six sites. Other influences on the Arctic hydrologic cycle, such as the strength of meridional transport, are assessed using the North Atlantic Oscillation index. We find that the independent, direct effect of sea ice on the increase of the percentage of Arctic sourced moisture (or Arctic moisture proportion, AMP) is 18.2 ± 4.6% and 10.8 ± 3.6%/100,000 km2 sea ice lost for each region, respectively, corresponding to increases of 10.9 ± 2.8% and 2.7 ± 1.1%/1 °C of warming in the vapor source regions. The moisture source changes likely result in increases of precipitation and changes in energy balance, creating significant uncertainty for climate predictions.

Researchers compared drought predictions for the second half of the 21st century with reconstructions of drought conditions dating back to the 11th century and found that the Central Plains and Southwest U.S. could experience the driest conditions in nearly a millennium. The results werepublished 12 February 2016 in Science Advances. The abstract concludes: “Notably, future drought risk will likely exceed even the driest centuries of the Medieval Climate Anomaly (1100-1300 CE) in both moderate (RCP 4.5) and high (RCP 8.5) future emissions scenarios, leading to drought conditions without precedent during the last millennium.” 

Unprecedented 21st-century drought risk in the American Southwest and Central Plains

""In the Southwest and Central Plains of Western North America, climate change is expected to increase drought severity in the coming decades. These regions nevertheless experienced extended Medieval-era droughts that were more persistent than any historical event, providing crucial targets in the paleoclimate record for benchmarking the severity of future drought risks. Here, we use an empirical drought reconstruction and three soil moisture metrics from 17 state-of-the-art general circulation models (GCMs) to show that these mod- els project a significantly drier later half of the 21st-century compared to the 20th-century and earlier paleoclimatic intervals. This desiccation is consistent across the majority of models regardless of the employed moisture balance variable, indicating a coherent and robust drying response to warming despite the diversity of models and metrics analyzed. Notably, future drought risk will likely exceed even the driest centuries of the Medieval Climate Anomaly (1100-1300 CE) in both moderate (RCP 4.5) and high (RCP 8.5) future emissions scenarios, leading to drought conditions without precedent during the last millennium.