Origins of the midlatitude Pacific decadal variability

Analysis of multiple climate simulations shows much of the midlatitude Pacific decadal variability to be composed of two simultaneously occurring elements: One is a stochastically driven, passive ocean response to the atmosphere while the other is oscillatory and represents a coupled mode of the ocean‐atmosphere system. ENSO processes are not required to explain the origins of the decadal variability. The stochastic variability is driven by random variations in wind stress and heat flux associated with internal atmospheric variability but amplified by a factor of 2 by interactions with the ocean. We also found a coupled mode of the ocean‐atmosphere system, characterized by a significant power spectral peak near 1 cycle/20 years in the region of the midlatitude North Pacific and Kuroshio Extension. Ocean dynamics appear to play a critical role in this coupled air/sea mode

The Ocean's Role in Continental Climate Variability and Change

A characteristic feature of global warming is the land-sea contrast, with stronger warming over land than over oceans. Recent studies find that this land-sea contrast also exists in equilibrium global change scenarios, and it is caused by differences in the availability of surface moisture over land and oceans. In this study it is illustrated that this land-sea contrast exists also on interannual time scales and that the ocean-land interaction is strongly asymmetric. The land surface temperature is more sensitive to the oceans than the oceans are to the land surface temperature, which is related to the processes causing the land-sea contrast in global warming scenarios. It suggests that the ocean's natural variability and change is leading to variability and change with enhanced magnitudes over the continents, causing much of the longer-time-scale (decadal) global-scale continental climate variability. Model simulations illustrate that continental warming due to anthropogenic forcing (e. g., the warming at the end of the last century or future climate change scenarios) is mostly (80%-90%) indirectly forced by the contemporaneous ocean warming, not directly by local radiative forcing

The North American Winter \u27Dipole\u27 and Extremes Activity: A CMIP5 Assessment

The 2013–2014 winter in North America brought intense drought in the West and severe cold in the East. The circulation anomalies were characterized as a dipole: an amplified upper-level ridge over the West Coast and a deepened trough over the central-eastern United States. A previous study using a single model has linked the dipole to the El Niño precursor and found that this link has strengthened in recent years. Here, 17 models from the Coupled Model Intercomparison Project Phase 5 are used to examine the dipole activity. Most models capture the dipole and its association with El Niño precursor and project this association to strengthen

A review of predictability studies of the Atlantic sector climate on decadal time-scales

This review paper discusses the physical basis and the potential for decadal climate predictability over the Atlantic and its adjacent land areas. Many observational and modeling studies describe pronounced decadal and multidecadal variability in the Atlantic Ocean. However, it still needs to be quantified to which extent the variations in the ocean drive variations in the atmosphere and over land. In particular, although a clear impact of the Tropics on the midlatitudes has been demonstrated, it is unclear if and how the extratropical atmosphere responds to midlatitudinal sea surface temperature anomalies. Although the mechanisms behind the decadal to multidecadal variability in the Atlantic sector are still controversial, there is some consensus that some of the longer-term multidecadal variability is driven by variations in the thermohaline circulation. The variations in the North Atlantic thermohaline circulation appear to be predictable one to two decades ahead, as shown by a number of perfect model predictability experiments. The next few decades will be dominated by these multidecadal variations, although the effects of anthropogenic climate change are likely to introduce trends. Some impact of the variations of the thermohaline circulation on the atmosphere has been demonstrated in some studies so that useful decadal predictions with economic benefit may be possible

The Practitioner's Dilemma: How to Assess the Credibility of Downscaled Climate Projections

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/101803/1/eost2013EO460005.pd

2,000-year-long temperature and hydrology reconstructions from the Indo-Pacific warm pool

Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature 460 (2009): 1113-1116, doi:10.1038/nature08233.Northern Hemisphere surface temperature reconstructions suggest that the late twentieth century was warmer than any other time during the past 500 years and possibly any time during the past 1,300 years. These temperature reconstructions are based largely on terrestrial records from extra-tropical or highelevation sites; however, global average surface temperature changes closely follow those of the global tropics, which are 75% ocean. In particular, the tropical Indo- Pacific warm pool (IPWP) represents a major heat reservoir that both influences global atmospheric circulation and responds to remote northern latitude forcings. Here we present a decadally resolved continuous sea surface temperature (SST) reconstruction from the IPWP that spans the past two millennia and overlaps the instrumental record, enabling both a direct comparison of proxy data to the instrumental record and an evaluation of past changes in the context of twentieth century trends. Our record from the Makassar Strait, Indonesia, exhibits trends that are similar to a recent Northern Hemisphere temperature reconstruction. Reconstructed SST was, however, within error of modern values during the Medieval Warm Period from about AD 1000 to AD 1250, towards the end of the Medieval Warm Period. SSTs during the Little Ice Age (approximately ad 1550–1850) were variable, and 0.5 to 1°C colder than modern values during the coldest intervals. A companion reconstruction of δ18O of sea water—a sea surface salinity and hydrology indicator— indicates a tight coupling with the East Asian monsoon system and remote control of IPWP hydrology on centennial–millennial timescales, rather than a dominant influence from local SST variation.This work was financially supported by the US NSF and the Ocean Climate Change Institute of WHOI

DOs and DON'Ts for using climate change information for water resource planning and management: guidelines for study design

Water managers are actively incorporating climate change information into their long- and short-term planning processes. This is generally seen as a step in the right direction because it supplements traditional methods, providing new insights that can help in planning for a non-stationary climate. However, the continuous evolution of climate change information can make it challenging to use available information appropriately. Advice on how to use the information is not always straightforward and typically requires extended dialogue between information producers and users, which is not always feasible. To help navigate better the ever-changing climate science landscape, this review is organized as a set of nine guidelines for water managers and planners that highlight better practices for incorporating climate change information into water resource planning and management. Each DOs and DON'Ts recommendation is given with context on why certain strategies are preferable and addresses frequently asked questions by exploring past studies and documents that provide guidance, including real-world examples mainly, though not exclusively, from the United States. This paper is intended to provide a foundation that can expand through continued dialogue within and between the climate science and application communities worldwide, a two-way information sharing that can increase the actionable nature of the information produced and promote greater utility and appropriate use