Research by AER Scientists Cited in IPCC Report on Climate Change

Fifteen research studies by AER scientists are referenced in Climate Change 2013: The Physical Science Basis, the Working Group I contribution to the U.N. IPCC's Fifth Assessment Report (WG1 AR5). The citations, which occur in 7 of the 14 chapters of the WGI AR5 report, are summarized here. Note: bold names indicate AER scientists. Underscored names worked at AER at the time the research was done and published.

Chapter 2: Observations: Atmosphere and Surface

Chapter 2 discusses stratospheric circulation and how it has changed in recent decades. The work of Cohen et al. (2009) is referenced showing that sudden stratospheric warmings have increased in the Arctic stratosphere over the past two decades.

Also in this chapter, Figure 2.37 and accompanying text describe the trends observed in surface winds. Notably the pattern of increased surface wind in the mid-Pacific is nearly identical in CCMP and OAFlux, two top blended data sets, but is misrepresented in the other data sets, including the various reanalyses. This analysis relies on Atlas et al., (2011), which described the background, algorithms used, availability, and example applications of the often cited CCMP ocean surface wind data set.

Chapter 3: Observations: Oceans

Chapter 3 discusses the difficulty in assessing the variability in critically important parameters such as ocean temperature and heat content over the full water column due to very poor sampling by current observing systems. The study by Ponte (2012) is referenced for its use of an eddy-resolving ocean state estimate to quantify the substantial variability in temperature and salinity expected in the deep ocean on time scales from months to years.

Chapter 7: Clouds and Aerosols

Chapter 7 discusses climate feedbacks due to cirrus clouds, including the dependence on ice particle size distributions. Cited is Mitchell et al. (2010), which detailed a method developed to remotely sense the concentrations of various sizes of ice particles.

The impact of aerosols on climate is also discussed in this chapter, including interactions between aerosols and clouds. Most global climate models include representations of aerosol-cloud interactions, and Quaas et al. (2009) is referenced for its comparison of aerosol-cloud-radiation relationships between ten general circulation models and satellite measurements that demonstrated both strengths and deficiencies of how these models represent these processes. The study of Liu et al. (2012) is cited for it description of the new modal aerosol model introduced in the global climate model CAM5 (Liu et al., 2012), which simulates aerosol size distributions, the mixing of aerosol components, aerosol properties and their complex interaction with cloud processes in a more realistic manner.

Chapter 8: Anthropogenic and Natural Radiative Forcing

Chapter 8 discusses the atmospheric radiative processes, a key element in climate change. Radiative transfer codes that accurately calculate the radiative impact of greenhouse gases and other atmospheric constituents are an essential component of the global climate models used to simulate present and future climate. AER’s radiative transfer codes are relied on throughout the atmospheric community, and Iacono et al. (2008) is cited for demonstrating their accuracy.

In addition, Chapter 8 references Oreopoulos et al. (2012) for its description of an international intercomparison of radiative transfer codes that was co-led by an AER scientist. This study compared radiative transfer code estimates to observed radiative fluxes in realistic atmospheric conditions and found generally good agreement. Another radiation code intercomparison, Forster et al. (2011), is also referenced in this chapter for its investigation of the performance of various radiative transfer codes.

Chapter 9: Evaluation of Climate Models

In the summary of climate model performance in Chapter 9 and expected future changes of climate patterns in Chapter 14, the report cites Furtado et al. (2011) for its comprehensive model evaluation of the Pacific modes of climate variability. This study shows that the coupled climate models have mixed results in reproducing the spatial and temporal characteristics of major observed Pacific climate patterns of variability (e.g., the Pacific Decadal Oscillation (PDO) and El Niño). In particular, the models struggle to accurately reproduce observed connections between El Niño in the tropical Pacific and PDO in the North Pacific, which leads to poorly simulated decadal climate variability in the models.

In discussion of evaluating climate model output with satellite measurments, Chapter 9 references the study of Iacono et al. (2003) that evaluated the climate model of the U.S. National Center for Atmospheric Research and identified biases related to water vapor and radiative processes.

Chapter 13: Observations: Sea Level Change

In discussion of the ocean mass component of sea level rise, Chapter 13 references the study of Quinn and Ponte (2010) that investigated errors and biases in the ocean mass trends estimated from data from the GRACE satellite. This study showed that the formal errors may not capture the true uncertainty in either regional or global ocean mass trends, particularly with regards to the glacial isostatic correction used.

Analyses of tide gauge and altimetry data by Vinogradov and Ponte (2011), which indicated the presence of considerably small spatial scale variability in annual mean sea level over many coastal regions, are an important factor for understanding the uncertainties in regional sea-level simulations and projections at sub-decadal time scales in coarse-resolution climate models that are also discussed in Chapter 13.

The paper by Tamisiea et al. (2010) examines how the exchange of water between the atmosphere, oceans, and continents can contribute to the water cycle, load the Earth and change its geoid, and cause the annual variations in relative sea level over the global ocean. The findings of a study by AER scientists were referenced in Chapter 13 as an example of geodynamic surface-loading models that can be used to describe the past and present changes in sea level caused by the redistribution of surface mass.

Chapter 14: Climate Phenomena and their Relevance for Future Regional Climate Change

Chapter 14 reports on the importance of different ‘flavors’ of El Niño on future regional climate change. Di Lorenzo et al. (2010) presents evidence of the unique impacts of Central Pacific (CPAC) El Niño events (i.e., El Niño episodes when the warmest waters are located in the central tropical Pacific) on the Northern Hemisphere atmospheric and oceanic circulation on interannual and decadal time scales. These circulation changes may become more prevalent in the future as the frequency of CPAC El Niño events may increase.

Note: bold names indicate AER scientists. Bold underscored names worked at AER at the time the research was done and published.