Two annual cycles of the Pacific cold tongue under orbital precession.

The Pacific cold tongue annual cycle in sea surface temperature is presumed to be driven by Earth's axial tilt1-5 (tilt effect), and thus its phasing should be fixed relative to the calendar. However, its phase and amplitude change dramatically and consistently under various configurations of orbital precession in several Earth System models. Here, we show that the cold tongue possesses another annual cycle driven by the variation in Earth-Sun distance (distance effect) from orbital eccentricity. As the two cycles possess slightly different periodicities6, their interference results in a complex evolution of the net seasonality over a precession cycle. The amplitude from the distance effect increases linearly with eccentricity and is comparable to the amplitude from the tilt effect for the largest eccentricity values over the last million years (e value approximately 0.05)7. Mechanistically, the distance effect on the cold tongue arises through a seasonal longitudinal shift in the Walker circulation and subsequent annual wind forcing on the tropical Pacific dynamic ocean-atmosphere system. The finding calls for reassessment of current understanding of the Pacific cold tongue annual cycle and re-evaluation of tropical Pacific palaeoclimate records for annual cycle phase changes.

Climate change: challenges and opportunities for global health.

IMPORTANCE: Health is inextricably linked to climate change. It is important for clinicians to understand this relationship in order to discuss associated health risks with their patients and to inform public policy. OBJECTIVES: To provide new US-based temperature projections from downscaled climate modeling and to review recent studies on health risks related to climate change and the cobenefits of efforts to mitigate greenhouse gas emissions. DATA SOURCES, STUDY SELECTION, AND DATA SYNTHESIS: We searched PubMed and Google Scholar from 2009 to 2014 for articles related to climate change and health, focused on governmental reports, predictive models, and empirical epidemiological studies. Of the more than 250 abstracts reviewed, 56 articles were selected. In addition, we analyzed climate data averaged over 13 climate models and based future projections on downscaled probability distributions of the daily maximum temperature for 2046-2065. We also compared maximum daily 8-hour average ozone with air temperature data taken from the National Oceanic and Atmospheric Administration, National Climate Data Center. RESULTS: By 2050, many US cities may experience more frequent extreme heat days. For example, New York and Milwaukee may have 3 times their current average number of days hotter than 32°C (90°F). High temperatures are also strongly associated with ozone exceedance days, for example, in Chicago, Illinois. The adverse health aspects related to climate change may include heat-related disorders, such as heat stress and economic consequences of reduced work capacity; respiratory disorders, including those exacerbated by air pollution and aeroallergens, such as asthma; infectious diseases, including vectorborne diseases and waterborne diseases, such as childhood gastrointestinal diseases; food insecurity, including reduced crop yields and an increase in plant diseases; and mental health disorders, such as posttraumatic stress disorder and depression, that are associated with natural disasters. Substantial health and economic cobenefits could be associated with reductions in fossil fuel combustion. For example, greenhouse gas emission policies may yield net economic benefit, with health benefits from air quality improvements potentially offsetting the cost of US and international carbon policies. CONCLUSIONS AND RELEVANCE: Evidence over the past 20 years indicates that climate change can be associated with adverse health outcomes. Health care professionals have an important role in understanding and communicating the related potential health concerns and the cobenefits from policies to reduce greenhouse gas emissions.

The role of aerosols in the evolution of tropical North Atlantic Ocean temperature anomalies.

Observations and models show that northern tropical Atlantic surface temperatures are sensitive to regional changes in stratospheric volcanic and tropospheric mineral aerosols. However, it is unknown whether the temporal variability of these aerosols is a key factor in the evolution of ocean temperature anomalies. We used a simple physical model, incorporating 26 years of satellite data, to estimate the temperature response of the ocean mixed layer to changes in aerosol loadings. Our results suggest that the mixed layer's response to regional variability in aerosols accounts for 69% of the recent upward trend, and 67% of the detrended and 5-year low pass-filtered variance, in northern tropical Atlantic Ocean temperatures.

Assessing risks of climate variability and climate change for Indonesian rice agriculture.

El Niño events typically lead to delayed rainfall and decreased rice planting in Indonesia's main rice-growing regions, thus prolonging the hungry season and increasing the risk of annual rice deficits. Here we use a risk assessment framework to examine the potential impact of El Niño events and natural variability on rice agriculture in 2050 under conditions of climate change, with a focus on two main rice-producing areas: Java and Bali. We select a 30-day delay in monsoon onset as a threshold beyond which significant impact on the country's rice economy is likely to occur. To project the future probability of monsoon delay and changes in the annual cycle of rainfall, we use output from the Intergovernmental Panel on Climate Change AR4 suite of climate models, forced by increasing greenhouse gases, and scale it to the regional level by using empirical downscaling models. Our results reveal a marked increase in the probability of a 30-day delay in monsoon onset in 2050, as a result of changes in the mean climate, from 9-18% today (depending on the region) to 30-40% at the upper tail of the distribution. Predictions of the annual cycle of precipitation suggest an increase in precipitation later in the crop year (April-June) of approximately 10% but a substantial decrease (up to 75% at the tail) in precipitation later in the dry season (July-September). These results indicate a need for adaptation strategies in Indonesian rice agriculture, including increased investments in water storage, drought-tolerant crops, crop diversification, and early warning systems.