Volcanic effects on climate

Volcanic eruptions which inject large amounts of sulfur-rich gas into the stratosphere produce dust veils which last years and cool the earth's surface. At the same time, these dust veils absorb enough solar radiation to warm the stratosphere. Since these temperature changes at the earth's surface and in the stratosphere are both in the opposite direction of hypothesized effects from greenhouse gases, they act to delay and mask the detection of greenhouse effects on the climate system. Tantalizing recent research results have suggested regional effects of volcanic eruptions, including effects on El Nino/Southern Oscillation (ENSO). In addition, a large portion of the global climate change of the past 100 years may be due to the effects of volcanoes, but a definite answer is not yet clear. While effects of several years were demonstrated with both data studies and numerical models, long-term effects, while found in climate model calculations, await confirmation with more realistic models. Extremely large explosive prehistoric eruptions may have produced severe weather and climate effects, sometimes called a 'volcanic winter'. Complete understanding of the above effects of volcanoes is hampered by inadequacies of data sets on volcanic dust veils and on climate change. Space observations can play an increasingly important role in an observing program in the future. The effects of volcanoes are not adequately separated from ENSO events, and climate modeling of the effects of volcanoes is in its infancy. Specific suggestions are made for future work to improve the knowledge of this important component of the climate system

Winter warming from large volcanic eruptions

An examination of the Northern Hemisphere winter surface temperature patterns after the 12 largest volcanic eruptions from 1883-1992 shows warming over Eurasia and North America and cooling over the Middle East which are significant at the 95 percent level. This pattern is found in the first winter after tropical eruptions, in the first or second winter after midlatitude eruptions, and in the second winter after high latitude eruptions. The effects are independent of the hemisphere of the volcanoes. An enhanced zonal wind driven by heating of the tropical stratosphere by the volcanic aerosols is responsible for the regions of warming, while the cooling is caused by blocking of incoming sunlight

Pinatubo eruption winter climate effects: Model versus observations

Large volcanic eruptions, in addition to the well-known effect of producing global cooling for a year or two, have been observed to produce shorter-term responses in the climate system involving non-linear dynamical processes. In this paper, we use the ECHAM2 general circulation model forced with stratospheric aerosols to test some of these ideas. Run in a perpetual-January mode, with tropical stratospheric heating from the volcanic aerosols typical of the 1982 El Chichon eruption or the 1991 Pinatubo eruption, we find a dynamical response with an increased polar night jet in the Northern Hemisphere (NH) and stronger zonal winds which extended down into the troposphere. The Azores High shifts northward with increased tropospheric westerlies at 60N and increased easterlies at 30N. Surface temperatures are higher both in northern Eurasia and North America, in agreement with observations for the NH winters or 1982-83 and 1991-92 as well as the winters following the other 10 largest volcanic eruptions since 1883

Spin-down of a stratified, rotating fluid,

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Meteorology, 1974.Bibliography: leaf 68.by Alan D. Robock.M.S

Climate predictability and simulation with a global climate model.

Thesis. 1977. Ph.D.--Massachusetts Institute of Technology. Dept. of Meteorology.Microfiche copy available in Archives and Science.Vita.Bibliography : leaves 206-218.Ph.D

Monitoring of Geoengineering Effects and their Natural and Anthropogenic Analogues

A number of climate intervention concepts, referred to as “geoengineering,” are being considered as a potential additional approach (beyond mitigation of greenhouse gas emissions) to manage climate change. However, before governments go down the path of attempting deliberate climate intervention including precursor field-experiments, it is essential that the scientific community take the necessary steps to validate our understanding that underpins any of the proposed intervention concepts in order to understand all likely consequences and put in place the necessary strategies for monitoring the expected and unintended consequences of such intervention. The Keck Institute for Space Studies (KISS) has sponsored a project to identify specific priorities for improved scientific understanding and focused efforts to address selected priorities. This project does not advocate the deployment of geoengineering, outdoor geoengineering experiments, or monitoring systems for such proposed geoengineering field experiments, but is rather a precautionary study with the following goals: 1) enumeration of where major gaps in our understanding exist in solar radiation management (SRM) approaches, 2) identification of the research that would be required to improve understanding of such impacts including modeling and observation of natural and anthropogenic analogues to geoengineering, and 3) a preliminary assessment of where gaps exist in observations of relevance to SRM and what is needed to fill such gaps. This project focuses primarily on SRM rather than other proposed geoengineering techniques such as carbon dioxide removal from the atmosphere because there exist a number of analogues to the SRM methods that currently operate on Earth that provide a unique opportunity to assess our understanding of the response of the climate system to associated changes in solar radiation. Additionally, the processes related to these analogues are also fundamental to understanding climate change itself being of central relevance to how climate is forced by aerosol and respond through clouds, among other influences. In other words, this research has likely powerful co-benefits for climate science writ large. The study phase of the project was executed in 2011 and consisted of two workshops at Caltech (May 23-26 and November 15-18) as well as several smaller meetings and telecons. Participants in the study included individuals with an established track record of geoengineering research (primarily modeling studies), experts in the theory and observation of related physical processes, as well as engineers with expertise in risk management and systems analysis. Graduate students and post-doctoral fellows were active participants in the study. Four major topics that were identified during the workshops as priorities for subsequent research and development, particularly in regards to addressing related observational gaps: 1. Volcanoes as analogues of geoengineering with stratospheric aerosols 2. Ship tracks and cloud/aerosol interactions in general as analogues of geoengineering with marine-cloud brightening 3. Studying more targeted geoengineering interventions to counteract specific consequences of climate change, and 4. Identifying the satellite-based albedo monitoring needs that would be required for monitoring either a geoengineering test or its natural and anthropogenic analogues. Major volcanic eruptions that inject sulfate aerosol into the stratosphere cool the planet and are one of the motivating examples behind geoengineering. Much more could be learned about the intentional introduction of stratospheric aerosols through a combination of more thorough analysis of existing data, and development of a rapid-response observing strategy to maximize what we can learn from a future large eruption. Gaps in our knowledge include the evolution of aerosol size, the interaction with cirrus, water vapor, and ozone, and tropospheric chemistry more broadly. There are also attribution challenges that need to be understood, as the conditions following volcanic eruptions are not the same as those due to SRM (e.g. the presence of ash, or the discrete vs continual injection). The second main concept put forth for geoengineering is to introduce aerosols (e.g. salt) to change the optical depth of marine clouds; the current analog for this effect is ship tracks and other cloud/aerosol interactions. There is potential for further analysis of existing data to better understand these interactions and assess the science behind this SRM approach. The sensitivities of cloud albedo to specific processes and parameters are poorly understood. There are also observational gaps, such as the entrainment rate, or direct measurement of albedo, that limit our current ability to assess this approach. Third, it is important to understand what the actual goals for a possible eventual implementation of SRM might be, since SRM would quite possibly be deployed in response to a particular concern, rather than a generic desire to restore the overall climate. The highest priority identified during the study program was to focus on the high risk, high impact potential for a “tipping point” associated with Arctic permafrost melt, and the potential for geoengineering to reverse this. Other tipping points involving Arctic sea-ice and the Greenland and Antarctic ice-sheets may also warrant targeted intervention studies. Finally, one of the specific gaps in our observational capability is the ability to monitor albedo accurately enough to measure and attribute changes, with sufficient spatial, spectral, and temporal resolution. This capability is needed for all of first three SRM topics

Appreciation of peer reviewers for 2015

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/133577/1/rog20102.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/133577/2/rog20102_am.pd

Sensitivity of Stratospheric Geoengineering with Black Carbon to Aerosol Size and Altitude of Injection

Simulations of stratospheric geoengineering with black carbon (BC) aerosols using a general circulation model with fixed sea surface temperatures show that the climate effects strongly depend on aerosol size and altitude of injection. 1 Tg BC/a injected into the lower stratosphere would cause little surface cooling for large radii but a large amount of surface cooling for small radii and stratospheric warming of over 60 C. With the exception of small particles, increasing the altitude of injection increases surface cooling and stratospheric warming. Stratospheric warming causes global ozone loss by up to 50% in the small radius case. The Antarctic shows less ozone loss due to reduction of polar stratospheric clouds, but strong circumpolar winds would enhance the Arctic ozone hole. Using diesel fuel to produce the aerosols is likely prohibitively expensive and infeasible. Although studying an absorbing aerosol is a useful counterpart to previous studies involving sulfate aerosols, black carbon geoengineering likely carries too many risks to make it a viable option for deployment

Thank You to Our 2018 Peer Reviewers

On behalf of the authors and readers of Reviews of Geophysics, the American Geophysical Union (AGU), and the broader scientific community, the Editors wish to wholeheartedly thank those who reviewed the manuscripts for Reviews of Geophysics in 2018. Reviews of Geophysics is the top rated journal in Geophysics and Geochemistry and it could not exist without your investment of time and effort, lending your expertise to ensure that the papers published in this journal meet the standards that the research community expects for it. We sincerely appreciate the time spent reading and commenting on manuscripts, and we are very grateful for your willingness and readiness to serve in this role. Reviews of Geophysics published 20 review papers and an editorial in 2018, covering most of the AGU Section topics, and for this we were able to rely on the efforts of 85 dedicated reviewers from 20 countries. Many reviewers answered the call multiple times. Thank you again. We look forward to a 2019 of exciting advances in the field and communicating those advances to our community and to the broader public