Explore the vast range of titles available.

\"Sixty-six million years ago an asteroid as large as Mt. Everest hit what is now the Yucatan Peninsula at a speed ten times faster than the fastest rifle bullet. Debris from the impact blew into space, re-entered the atmosphere as a swarm of shooting stars that burned the global forests and grasslands, leaving behind a thin global layer containing rock from the asteroid and from Mexico, and smoke from the fires. This layer marks one of the greatest extinctions in Earth history including not just dinosaurs, but also fish, plankton, ammonites, and plants making up about 75% of the known species. The major culprits in these extinctions are loss of sunlight due to absorption by the smoke and decade-long ice age temperatures. A nuclear war with just a few hundred of the world's 12,000 nuclear weapons targeted on densely populated cities could plunge Earth into the same types of conditions that the dinosaurs experienced. Even a war between India and Pakistan could kill 1 to 3 billion people from starvation due to agricultural failure, while 6 billion people might starve following a war involving Russia, NATO, and the U.S.The book describes how the dinosaurs died, and how their deaths parallel what might happen to people after a nuclear war. The book reflects on the odds of future asteroid impacts, how to stop them, and ends with what the readers personally and together can do to prevent a nuclear war, so that humans don't end up like the dinosaurs.\" -- publisher website 20250725

This study evaluates different hypotheses of the origin of the Little Ice Age, focusing on the long-term response of Arctic sea ice and oceanic circulation to solar and volcanic perturbations. The authors analyze the Last Millennium Ensemble of climate model simulations carried out with the Community Earth System Model at the National Center for Atmospheric Research. The authors examine the duration and strength of volcanic perturbations, and the effects of initial and boundary conditions, such as the phase of the Atlantic multidecadal oscillation. They evaluate the impacts of these factors on decadal-to-multicentennial perturbations of the cryospheric, oceanic, and atmospheric components of the climate system. The authors show that, at least in the Last Millennium Ensemble, volcanic eruptions are followed by a decadal-scale positive response of the Atlantic multidecadal overturning circulation, followed by a centennial-scale enhancement of the Northern Hemispheric sea ice extent. It is hypothesized that a few mechanisms, not just one, may have to play a role in consistently explaining such a simulated climate response at both decadal and centennial time scales. The authors argue that large volcanic forcing is necessary to explain the origin and duration of Little Ice Age–like perturbations in the Last Millennium Ensemble. Other forcings might play a role as well. In particular, prolonged fluctuations in solar irradiance associated with solar minima potentially amplify the enhancement of the magnitude of volcanically triggered anomalies of Arctic sea ice extent.

Injecting sulfate aerosol precursors into the stratosphere has been suggested as a means of geoengineering to cool the planet and reduce global warming. The decision to implement such a scheme would require a comparison of its benefits, dangers, and costs to those of other responses to global warming, including doing nothing. Here we evaluate those factors for stratospheric geoengineering with sulfate aerosols. Using existing U.S. military fighter and tanker planes, the annual costs of injecting aerosol precursors into the lower stratosphere would be several billion dollars. Using artillery or balloons to loft the gas would be much more expensive. We do not have enough information to evaluate more exotic techniques, such as pumping the gas up through a hose attached to a tower or balloon system. Anthropogenic stratospheric aerosol injection would cool the planet, stop the melting of sea ice and land‐based glaciers, slow sea level rise, and increase the terrestrial carbon sink, but produce regional drought, ozone depletion, less sunlight for solar power, and make skies less blue. Furthermore it would hamper Earth‐based optical astronomy, do nothing to stop ocean acidification, and present many ethical and moral issues. Further work is needed to quantify many of these factors to allow informed decision‐making.

Extreme East Asian summer monsoon (EASM) rainfall frequently induces floods that threaten millions of people, and has been generally attributed to internal climate variability. In contrast to the hydrological weakening theory of volcanic eruptions, here we present convergent empirical and modeling evidence for significant intensification of EASM rainfall in response to strong tropical volcanic eruptions. Our multi-proxy analyses show a significantly increased EASM in the first summer after tropical eruptions from 1470 AD to the present, and the more frequent occurrence of El Niños in the first boreal winter after eruptions is necessary for the enhanced EASM. Model simulation ensembles show that a volcano-induced El Niño and the associated stronger than non-volcanic El Niño warm pool air-sea interaction intensify EASM precipitation, overwhelming volcanic-induced moisture deficiency. This work sheds light on the intertwined relationship between external forcing and internal climate variability and potential flood disasters resulting from tropical volcanic eruptions. The probability of an El Niño in the winter after large tropical volcanic eruptions increases. When this happens, summer monsoon precipitation over East Asia is enhanced, overwhelming thermodynamic precipitation reduction from volcanic cooling.

Research on albedo enhancement by stratospheric sulfur injection inspired by Paul Crutzen's paper a decade ago has made clear that it may present serious risks and concerns as well as benefits if used to address the global warming problem. While volcanic eruptions were suggested as innocuous examples of stratospheric aerosols cooling the planet, the volcano analog also argues against stratospheric geoengineering because of ozone depletion and regional hydrologic responses. Continuous injection of SO2 into the lower stratosphere would reduce global warming and some of its negative impacts, and would increasing the uptake of CO2 by plants, but research in the past decade has pointed out a number of potential negative impacts of stratospheric geoengineering. More research is needed to better quantify the potential benefits and risks so that if society is tempted to implement geoengineering in the future it will be able to make an informed decision. Key Points Paul Crutzen warned the world about dangerous global warming and inspired important geoengineering research in 2006 Stratospheric geoengineering could present a number of risks and concerns as well as benefits, but there are still many issues to address More research on geoengineering is needed so that if society is tempted to implement geoengineering, it will be an informed decision Plain Language Summary Global warming is a real problem for society. Using the atmosphere as a sewer for the gases produced by burning coal, oil, and natural gas (fossil fuels) and by making cement, will produce dangerous impacts. Ten years ago Paul Crutzen suggested that society should consider creating a cloud in the upper atmosphere to reflect sunlight and cool Earth, as he saw little action on reducing the emissions of the greenhouse gases that are causing global warming. In the decade since then, climate modeling and studying volcanic eruptions have made it clear that this “geoengineering solution” would present its own dangerous impacts, and perhaps make the situation even worse. This would include impacts on precipitation patterns which might affect our food supply and ozone depletion, which would result in more dangerous ultraviolet radiation. Clearly the solution is to leave the fossil fuels in the ground and switch to solar and wind power, but as our energy system is transformed, we may be tempted to do some geoengineering in the meantime to reduce the most dangerous aspects of global warming. We need more research so that any such choice will be an informed decision, taking into account both the benefits and risks.

The ability of the climate models submitted to the Coupled Model Intercomparison Project 5 (CMIP5) database to simulate the Northern Hemisphere winter climate following a large tropical volcanic eruption is assessed. When sulfate aerosols are produced by volcanic injections into the tropical stratosphere and spread by the stratospheric circulation, it not only causes globally averaged tropospheric cooling but also a localized heating in the lower stratosphere, which can cause major dynamical feedbacks. Observations show a lower stratospheric and surface response during the following one or two Northern Hemisphere (NH) winters, that resembles the positive phase of the North Atlantic Oscillation (NAO). Simulations from 13 CMIP5 models that represent tropical eruptions in the 19th and 20th century are examined, focusing on the large‐scale regional impacts associated with the large‐scale circulation during the NH winter season. The models generally fail to capture the NH dynamical response following eruptions. They do not sufficiently simulate the observed post‐volcanic strengthened NH polar vortex, positive NAO, or NH Eurasian warming pattern, and they tend to overestimate the cooling in the tropical troposphere. The findings are confirmed by a superposed epoch analysis of the NAO index for each model. The study confirms previous similar evaluations and raises concern for the ability of current climate models to simulate the response of a major mode of global circulation variability to external forcings. This is also of concern for the accuracy of geoengineering modeling studies that assess the atmospheric response to stratosphere‐injected particles. Key Points Large volcanic eruptions cause a major dynamical response in the atmosphere CMIP5 models are assessed for their ability to simulate this response No models in the CMIP5 database sufficiently represent this response

We test how the time of year of a large Arctic volcanic eruption determines the climate impacts by conducting simulations with a general circulation model of Earth's climate. For eruptions injecting less than about 3 Tg of SO2 into the lower stratosphere, we expect no detectable climatic effect, no matter what the season of the eruption. For an injection of 5 Tg of SO2 into the lower stratosphere, an eruption in the summer would cause detectable climate effects, whereas an eruption at other times of the year would cause negligible effects. This is mainly due to the seasonal variation in insolation patterns and sulfate aerosol deposition rates. In all cases, the sulfate aerosols that form get removed from the atmosphere within a year after the eruption by large‐scale deposition. Our simulations of a June eruption have many similar features to previous simulations of the eruption of Katmai in 1912, including some amount of cooling over Northern Hemisphere continents in the summer of the eruption, which is an expected climate response to large eruptions. Previous Katmai simulations show a stronger climate response, which we attribute to differences in choices of climate model configurations, including their specification of sea surface temperatures rather than the use of a dynamic ocean model as in the current simulations.

Stratospheric aerosols from large tropical explosive volcanic eruptions backscatter shortwave radiation and reduce the global mean surface temperature. Observations suggest that they also favour an El Niño within 2 years following the eruption. Modelling studies have, however, so far reached no consensus on either the sign or physical mechanism of El Niño response to volcanism. Here we show that an El Niño tends to peak during the year following large eruptions in simulations of the Fifth Coupled Model Intercomparison Project (CMIP5). Targeted climate model simulations further emphasize that Pinatubo-like eruptions tend to shorten La Niñas, lengthen El Niños and induce anomalous warming when occurring during neutral states. Volcanically induced cooling in tropical Africa weakens the West African monsoon, and the resulting atmospheric Kelvin wave drives equatorial westerly wind anomalies over the western Pacific. This wind anomaly is further amplified by air–sea interactions in the Pacific, favouring an El Niño-like response. El Niño tends to follow 2 years after volcanic eruptions, but the physical mechanism behind this phenomenon is unclear. Here the authors use model simulations to show that a Pinatubo-like eruption cools tropical Africa and drives westerly wind anomalies in the Pacific favouring an El Niño response.

It has been suggested that increased stratospheric sulfate aerosol loadings following large, low latitude volcanic eruptions can lead to wintertime warming over Eurasia through dynamical stratosphere–troposphere coupling. We here investigate the proposed connection in the context of hypothetical future stratospheric sulfate geoengineering in the Geoengineering Large Ensemble simulations. In those geoengineering simulations, we find that stratospheric circulation anomalies that resemble the positive phase of the Northern Annular Mode in winter are a distinguishing climate response which is absent when increasing greenhouse gases alone are prescribed. This stratospheric dynamical response projects onto the positive phase of the North Atlantic Oscillation, leading to associated side effects of this climate intervention strategy, such as continental Eurasian warming and precipitation changes. Seasonality is a key signature of the dynamically driven surface response. We find an opposite response of the North Atlantic Oscillation in summer, when no dynamical role of the stratosphere is expected. The robustness of the wintertime forced response stands in contrast to previously proposed volcanic responses.

Using Hadley Global Environment Model 2 - Earth System and Max Planck Institute Earth System Model simulations, we assess the impact of global warming and stratospheric geoengineering on deciduous fruit production in Himachal Pradesh (the second-largest apple-producing state in India). The impacts have been assessed for the Representative Concentration Pathways 4.5 (RCP4.5) global warming scenario, and a corresponding geoengineered scenario (G3) from the Geoengineering Model Intercomparison Project, in which stratospheric aerosols are increased for 50 years from 2020 through 2069 to balance the global warming radiative forcing, and then aerosol precursor emissions are terminated. We used the period 2055–2069 (with the largest geoengineering forcing) and the period 2075–2089 (beginning 5 years into the termination phase) and evaluated winter chill and growing season heat accumulation. We found that although stratospheric geoengineering would be able to suppress the increase in temperature under an RCP4.5 scenario to some extent during both switch-on and switch-off periods, if the geoengineering was terminated, the rate of temperature increase would be higher than RCP4.5. The agroclimatically suitable area is projected to shift northeastwards (to higher elevations) under RCP4.5 as well as G3 during both periods. However, during the switched on period, geoengineering would restrict the shift, and areas of Shimla and Mandi districts (most suitable under the current climate) would not be lost due to global warming. Even during the switched off period, before the climate returned to RCP4.5 levels, the above areas would, although to a lesser extent, have reduced harmful climate effects from global warming. However, the area of suitable land (the intersection of soil and agroclimatic suitability) would decrease in both periods for RCP4.5 as well as G3, because as more high-elevation regions become agroclimatically suitable, they do not have suitable soils to support cultivation. Geoengineering could benefit deciduous fruit production by reducing the intensity of global warming; however, if geoengineering was terminated abruptly, the rate of change in temperature would be quite high. This could lead to a rapid change in land suitability and might result in total crop failure in a shorter period compared to RCP4.5.