Are changes in global precipitation constrained by the tropospheric energy budget?

Copyright © 2009 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act September 2010 Page 2 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108, as revised by P.L. 94-553) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a web site or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. Additional details are provided in the AMS Copyright Policy, available on the AMS Web site located at (http://www.ametsoc.org/) or from the AMS at 617-227-2425 or [email protected] tropospheric energy budget argument is used to analyze twentieth-century precipitation changes. It is found that global and ocean-mean general circulation model (GCM) precipitation changes can be understood as being due to the competing direct and surface-temperature-dependent effects of external climate forcings. In agreement with previous work, precipitation is found to respond more strongly to anthropogenic and volcanic sulfate aerosol and solar forcing than to greenhouse gas and black carbon aerosol forcing per unit temperature. This is due to the significant direct effects of greenhouse gas and black carbon forcing. Given that the relative importance of different forcings may change in the twenty-first century, the ratio of global precipitation change to global temperature change may be quite different. Differences in GCM twentieth- and twenty-first-century values are tractable via the energy budget framework in some, but not all, models. Changes in land-mean precipitation, on the other hand, cannot be understood at all with the method used here, even if land–ocean heat transfer is considered. In conclusion, the tropospheric energy budget is a useful concept for understanding the precipitation response to different forcings but it does not fully explain precipitation changes even in the global mean

The myriad challenges of the Paris Agreement

The much awaited and intensely negotiated Paris Agreement was adopted on 12 December 2015 by the Parties to the United Nations Framework Convention on Climate Change. The agreement set out a more ambitious long-term temperature goal than many had anticipated, implying more stringent emissions reductions that have been under-explored by the research community. By its very nature a multidisciplinary challenge, filling the knowledge gap requires not only climate scientists, but the whole Earth system science community, as well as economists, engineers, lawyers, philosophers, politicians, emergency planners and others to step up. To kick start cross-disciplinary discussions, the University of Oxford's Environmental Change Institute focused its 25th anniversary conference upon meeting the challenges of the Paris Agreement for science and society. This theme issue consists of review papers, opinion pieces and original research from some of the presentations within that meeting, covering a wide range of issues underpinning the Paris Agreement

Correction to: “Constraining climate forecasts: The role of prior assumptions”

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Certificates for CCS at reduced public cost: securing the UK's energy and climate future, Energy Bill 2015

This Paper concerns the Energy Bill, which starts its Committee stages in the Lords on Monday 7th September and Wednesday 9th September 2015. The Bill is mainly tasked to create the OGA (Oil and Gas Authority). In addition the Bill creates responsibilities for the OGA regarding Carbon Capture and Storage (CCS) licensing. Most importantly, the Bill raises the opportunity for a discussion of how the envisaged development of CCS will be paid for. At present, the funding model involves significant taxpayer support through the CCS competition and levy control framework on electricity. We make a simple proposal that would remove this burden of Government support, and spread the cost of CCS development and deployment across the entire fossil fuel sector through a Certificate scheme that would rely only on data already reported to Government and the OGA, thus minimising the costs of compliance.This Paper concerns the Energy Bill, which starts its Committee stages in the Lords on Monday 7th September and Wednesday 9th September 2015. The Bill is mainly tasked to create the OGA (Oil and Gas Authority). In addition the Bill creates responsibilities for the OGA regarding Carbon Capture and Storage (CCS) licensing. Most importantly, the Bill raises the opportunity for a discussion of how the envisaged development of CCS will be paid for. At present, the funding model involves significant taxpayer support through the CCS competition and levy control framework on electricity. We make a simple proposal that would remove this burden of Government support, and spread the cost of CCS development and deployment across the entire fossil fuel sector through a Certificate scheme that would rely only on data already reported to Government and the OGA, thus minimising the costs of compliance

Quantifying non-CO2 contributions to remaining carbon budgets

The IPCC Special Report on 1.5 °C concluded that anthropogenic global warming is determined by cumulative anthropogenic CO2 emissions and the non-CO2 radiative forcing level in the decades prior to peak warming. We quantify this using CO2-forcing-equivalent (CO2-fe) emissions. We produce an observationally constrained estimate of the Transient Climate Response to cumulative carbon Emissions (TCRE), giving a 90% confidence interval of 0.26–0.78 °C/TtCO2, implying a remaining total CO2-fe budget from 2020 to 1.5 °C of 350–1040 GtCO2-fe, where non-CO2 forcing changes take up 50 to 300 GtCO2-fe. Using a central non-CO2 forcing estimate, the remaining CO2 budgets are 640, 545, 455 GtCO2 for a 33, 50 or 66% chance of limiting warming to 1.5 °C. We discuss the impact of GMST revisions and the contribution of non-CO2 mitigation to remaining budgets, determining that reporting budgets in CO2-fe for alternative definitions of GMST, displaying CO2 and non-CO2 contributions using a two-dimensional presentation, offers the most transparent approach

Uncertainties in mitigating aviation non-CO2 emissions for climate and air quality using hydrocarbon fuels

The uncertainties over the effects of aviation non-CO2 emissions on climate and air quality are assessed in the context of potential mitigation measures for liquid hydrocarbon fuels. Aviation non-CO2 emissions that affect climate include nitrogen oxides (NOx), aerosol particles (soot and sulphur-based), and water vapour. Water vapour and aerosols have small direct radiative effects but are also involved in the formation of contrails and contrail cirrus, currently, the largest non-CO2 effect on climate. These non-CO2 effects on climate are quantified with low confidence, compared to that of CO2, which is quantified with high confidence. The sign of the NOx radiative effects may change from positive to negative. The effects of soot and sulphur emissions on cloudiness are very poorly understood and studies indicate forcings that range from large negative through to small positive. NOx and soot emissions can be reduced through changes in combustion technology but have tradeoffs with each other and CO2. Soot can also be reduced through reduced aromatic content of fuels. In all cases, there are complex choices to be made because of tradeoffs between species, and CO2. Contrail cirrus and soot aerosol–cloud interactions potentially have opposing signs but are both related to soot emissions (at present) and need to be considered together in mitigation strategies. Because of the uncertainties and tradeoffs involved, it is problematic to recommend definitive courses of action on aviation non-CO2 emissions since they may be of limited effect or have unintended consequences. Aviation's non-CO2 effects on climate are short-term, as opposed to those of CO2, which last millennia. If aviation is to contribute towards restricting anthropogenic surface warming to 1.5 or 2 °C then reduction of emissions of CO2 from fossil fuels remains the top priority. In terms of air quality, the situation is more straightforward with emissions standards being set by the International Civil Aviation Organization for NOx and non-volatile particulate matter (and other minor species), which need to be complied with