Impact of Global Climate Change on Pulmonary Health: Susceptible and Vulnerable Populations.

As fossil fuel combustion continues to power the global economy, the rate of climate change is accelerating, causing severe respiratory health impacts and large disparities in the degree of human suffering. Hotter and drier climates lead to longer and more severe wildland fire seasons, impairing air quality around the globe. Hotter temperatures lead to higher amounts of ozone and particles, causing the exacerbation of chronic respiratory diseases and premature mortality. Longer pollen seasons and higher pollen concentrations provoke allergic airway diseases. In arid regions, accelerated land degradation and desertification are promoting dust pollution and impairing food production and nutritional content that are essential to respiratory health. Extreme weather events and flooding impede healthcare delivery and can lead to poor indoor air quality due to mold overgrowth. Climate and human activities that harm the environment and ecosystem may also affect the emergence and spread of viral infections, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and associated morbidity and mortality exacerbated by air pollution. Children and elderly individuals are more susceptible to the adverse health effects of climate change. Geographical and socioeconomic circumstances, together with a decreased capacity to adapt, collectively increase vulnerability to the adverse effects of climate change. Successful mitigation of anthropogenic climate change is dependent on the commitment of energy-intensive nations to manage greenhouse gas emissions, as well as societal support and response to aggravating factors. In this review, we focus on the respiratory health impacts of global climate change, with an emphasis on susceptible and vulnerable populations and low- and middle-income countries.

Considering thermal-viscous collapse of the Greenland ice sheet.

We explore potential changes in Greenland ice sheet form and flow associated with increasing ice temperatures and relaxing effective ice viscosities. We define "thermal-viscous collapse" as a transition from the polythermal ice sheet temperature distribution characteristic of the Holocene to temperate ice at the pressure melting point and associated lower viscosities. The conceptual model of thermal-viscous collapse we present is dependent on: (1) sufficient energy available in future meltwater runoff, (2) routing of meltwater to the bed of the ice sheet interior, and (3) efficient energy transfer from meltwater to the ice. Although we do not attempt to constrain the probability of thermal-viscous collapse, it appears thermodynamically plausible to warm the deepest 15% of the ice sheet, where the majority of deformational shear occurs, to the pressure melting point within four centuries. First-order numerical modeling of an end-member scenario, in which prescribed ice temperatures are warmed at an imposed rate of 0.05 K/a, infers a decrease in ice sheet volume of 5 ± 2% within five centuries of initiating collapse. This is equivalent to a cumulative sea-level rise contribution of 33 ± 18 cm. The vast majority of the sea-level rise contribution associated with thermal-viscous collapse, however, would likely be realized over subsequent millennia.

End of the Little Ice Age in the Alps forced by industrial black carbon.

Glaciers in the European Alps began to retreat abruptly from their mid-19th century maximum, marking what appeared to be the end of the Little Ice Age. Alpine temperature and precipitation records suggest that glaciers should instead have continued to grow until circa 1910. Radiative forcing by increasing deposition of industrial black carbon to snow may represent the driver of the abrupt glacier retreats in the Alps that began in the mid-19th century. Ice cores indicate that black carbon concentrations increased abruptly in the mid-19th century and largely continued to increase into the 20th century, consistent with known increases in black carbon emissions from the industrialization of Western Europe. Inferred annual surface radiative forcings increased stepwise to 13-17 W⋅m(-2) between 1850 and 1880, and to 9-22 W⋅m(-2) in the early 1900s, with snowmelt season (April/May/June) forcings reaching greater than 35 W⋅m(-2) by the early 1900s. These snowmelt season radiative forcings would have resulted in additional annual snow melting of as much as 0.9 m water equivalent across the melt season. Simulations of glacier mass balances with radiative forcing-equivalent changes in atmospheric temperatures result in conservative estimates of accumulating negative mass balances of magnitude -15 m water equivalent by 1900 and -30 m water equivalent by 1930, magnitudes and timing consistent with the observed retreat. These results suggest a possible physical explanation for the abrupt retreat of glaciers in the Alps in the mid-19th century that is consistent with existing temperature and precipitation records and reconstructions.

Large fluctuations in speed on Greenland's Jakobshavn Isbrae glacier.

It is important to understand recent changes in the velocity of Greenland glaciers because the mass balance of the Greenland Ice Sheet is partly determined by the flow rates of these outlets. Jakobshavn Isbrae is Greenland's largest outlet glacier, draining about 6.5 per cent of the ice-sheet area, and it has been surveyed repeatedly since 1991 (ref. 2). Here we use remote sensing data to measure the velocity of Jakobshavn Isbrae between 1992 and 2003. We detect large variability of the velocity over time, including a slowing down from 6,700 m yr(-1) in 1985 to 5,700 m yr(-1) in 1992, and a subsequent speeding up to 9,400 m yr(-1) by 2000 and 12,600 m yr(-1) in 2003. These changes are consistent with earlier evidence for thickening of the glacier in the early 1990s and rapid thinning thereafter. Our observations indicate that fast-flowing glaciers can significantly alter ice discharge at sub-decadal timescales, with at least a potential to respond rapidly to a changing climate.

Surface melt-induced acceleration of Greenland ice-sheet flow.

Ice flow at a location in the equilibrium zone of the west-central Greenland Ice Sheet accelerates above the midwinter average rate during periods of summer melting. The near coincidence of the ice acceleration with the duration of surface melting, followed by deceleration after the melting ceases, indicates that glacial sliding is enhanced by rapid migration of surface meltwater to the ice-bedrock interface. Interannual variations in the ice acceleration are correlated with variations in the intensity of the surface melting, with larger increases accompanying higher amounts of summer melting. The indicated coupling between surface melting and ice-sheet flow provides a mechanism for rapid, large-scale, dynamic responses of ice sheets to climate warming.