We often use feedback terminology to help us understand why models differ in their estimates of the magnitude of the surface temperature changes produced by a given change in the Earth’s energy balance, such as that due to an increase in carbon dioxide. But several lines of evidence have suggested that the methodology used to define these feedbacks is far from optimal, making the typical model’s behavior look more complicated than it really is. Our goal in this short note was to propose an alternative methodology that simplifies the analysis in several ways. Read More…
The fifth phase of the Coupled Model Intercomparison Project (CMIP5) will produce a coordinated multi-model dataset that is designed to advance our knowledge of climate variability and climate change. Researchers worldwide will analyze the model output and produce results that will underlie the forthcoming IPCC Fifth Assessment Report. Unprecedented in scale, CMIP5 has attracted participation from all major climate modeling groups. Building on previous CMIP efforts, CMIP5 includes “long-term” simulations of 20th century climate and projections for the 21st century and beyond . Read More…
Oxygen minimum zones (OMZs) exclude many classes of the biological community and are major sites of fixed nitrogen removal from the open ocean. Previous estimates of rates of fixed nitrogen loss through denitrification in the pelagic ocean and in sediments have been unable to match estimates of the supply of fixed nitrogen via N2 fixation, rivers, and atmospheric deposition. This has led some scientists to the conclusion that the global ocean nitrogen cycle is out of balance, and the oceans are accumulating fixed nitrogen. However, commonly-used gridded data sets such as the World Ocean Atlas (WOA) tend to overestimate the concentration of O2 compared to measurements in grids 1 where O2 falls in the suboxic range (O2 < 2 – 10 μM), thereby underestimating the extent of O2 depletion in OMZs. Read More…
The goal of this research is to evaluate the fidelity of GFDL climate models in reproducing the characteristics of summertime heat waves in North America, and to examine the model-projected changes of these characteristics in the 21st century.
North American incurs considerable economic costs due to heat waves. Understanding of the processes contributing to heat waves, and projecting changes in their characteristics in the 21st century, are an integral part of the NOAA mission to provide scientific information on the present and future states of the climate system. Read More…
As Asian countries develop, they are emitting more ozone precursors that pollute surface level air. Many studies have documented this pollution being carried by air currents to the western United States. To determine the extent to which this pollution is affecting air quality in the western U.S., we analyzed balloon soundings, aircraft, surface and satellite measurements from May through June 2010 using a new global high-resolution chemistry-climate model. Our findings indicate that Asian pollution contributes as much as 20 percent of total ozone during springtime pollution episodes in western U.S. surface air. Read More…
Ten percent of today’s ocean volume is characterized by low level of dissolved oxygen similar to those found in the well-known “dead zones” in the Gulf of Mexico with 35% of global surface waters overlying at least some of this “hypoxia” (O2 < 88 µM;2ml l-1). Under global warming, higher temperatures would be expected to directly lower oxygen concentrations and enhanced stratification to reduce the flow of well-ventilated surface waters to the interior. Under such circumstances, it has been hypothesized that the open-ocean dead zones could greatly expand and indeed changes in low-oxygen waters have been invoked as evidence of climate change. Read More…
One aspect of uncertainty in future projections of basin-wide hurricane activity stems from the variety of projections of the spatial pattern of tropical warming. A high-resolution, global atmospheric model is used to explore hurricane frequency response to sea surface temperature (SST) anomalies generated by coupled models for the late 21st century using the SRES A1B scenario. Read More…
There is considerable uncertainty in projections of the impacts of climate on fisheries yields due to uncertainties in climate change impacts on primary production and the processes controlling how much primary production is transferred to fish. Primary production and proxies such as chlorophyll have proven to be useful predictors of fisheries yields at regional scales but show much less skill when applied globally. The marine food web dynamics that control the transfer of energy from phytoplankton to fish are complex and the relationship between primary production and fisheries production may differ dramatically between ecosystems due to changes in planktonic food web structure. Read More…
An important part of the global water cycle, the South Asian summer monsoon provides about 80% of the region’s annual precipitation, and touches the lives of more than 20% of the world’s population. Using the NOAA/GFDL state-of-the-art global climate model that accounts for all the known natural and anthropogenic forcings, we have investigated what caused the observed decrease in the South Asian summer monsoon rainfall over the second half of the 20th century. Was the widespread drying due to natural factors or human activities? If the latter, what were the relative contributions of anthropogenic greenhouse gases and aerosols? Answering these questions poses a challenging test on our fundamental knowledge of the changes to the Earth’s hydrological cycle, and on our ability to understand and project future regional climate change. Read More…
Surface-based inversions (SBI) are frequent features of the Arctic and Antarctic atmospheric boundary layer and influence important climate processes. However, prior to this study, climatological polar SBI properties had not been fully characterized, nor had climate model simulations of SBIs been compared comprehensively to observations. Using 20 years of radiosonde observations, and simulations from two state-of-the-art climate models, this study examines the spatial and temporal variability of three SBI characteristics – frequency of occurrence, depth (from the surface to the inversion top), and intensity (temperature difference over the SBI depth) – and relationships among them. Read More…
