scholarly journals Hydrogen-Nitrogen Greenhouse Warming in Earth's Early Atmosphere

Science ◽  
2013 ◽  
Vol 339 (6115) ◽  
pp. 64-67 ◽  
Author(s):  
Robin Wordsworth ◽  
Raymond Pierrehumbert
Keyword(s):  
Atmospheric Composition ◽  
Early Earth ◽  
Greenhouse Warming ◽  
Mixing Ratio ◽  
The Past ◽  
Early Atmosphere ◽  
Global Cooling ◽  
Surface Liquid ◽  
Atmospheric Mass ◽  
Global Mean

Understanding how Earth has sustained surface liquid water throughout its history remains a key challenge, given that the Sun’s luminosity was much lower in the past. Here we show that with an atmospheric composition consistent with the most recent constraints, the early Earth would have been significantly warmed by H2-N2collision–induced absorption. With two to three times the present-day atmospheric mass of N2and a H2mixing ratio of 0.1, H2-N2warming would be sufficient to raise global mean surface temperatures above 0°C under 75% of present-day solar flux, with CO2levels only 2 to 25 times the present-day values. Depending on their time of emergence and diversification, early methanogens may have caused global cooling via the conversion of H2and CO2to CH4, with potentially observable consequences in the geological record.

scholarly journals On the probability of habitable planets

2013 ◽  
Vol 12 (3) ◽  
pp. 177-185 ◽  
Author(s):  
François Forget
Keyword(s):  
Liquid Water ◽  
Climate Models ◽  
Climatic Conditions ◽  
Point Of View ◽  
Habitable Zone ◽  
One Dimensional ◽  
The Past ◽  
Surface Liquid ◽  
New Generation ◽  
Global Mean

AbstractIn the past 15 years, astronomers have revealed that a significant fraction of the stars should harbour planets and that it is likely that terrestrial planets are abundant in our galaxy. Among these planets, how many are habitable, i.e. suitable for life and its evolution? These questions have been discussed for years and we are slowly making progress. Liquid water remains the key criterion for habitability. It can exist in the interior of a variety of planetary bodies, but it is usually assumed that liquid water at the surface interacting with rocks and light is necessary for emergence of a life able to modify its environment and evolve. The first key issue is thus to understand the climatic conditions allowing surface liquid water assuming a suitable atmosphere. These have been studied with global mean one-dimensional (1D) models which have defined the ‘classical habitable zone’, the range of orbital distances within which worlds can maintain liquid water on their surfaces (Kasting et al. 1993). A new generation of 3D climate models based on universal equations and tested on bodies in the solar system are now available to explore with accuracy climate regimes that could locally allow liquid water. The second key issue is now to better understand the processes which control the composition and the evolution of the atmospheres of exoplanets, and in particular the geophysical feedbacks that seem to be necessary to maintain a continuously habitable climate. From that point of view, it is not impossible that the Earth's case may be special and uncommon.

Modelling palaeophotosynthesis: late Cretaceous to present

1994 ◽  
Vol 346 (1318) ◽  
pp. 421-432 ◽  
Keyword(s):  
Late Cretaceous ◽  
Atmospheric Composition ◽  
Photosynthetic Rates ◽  
The Past ◽  
Global Cooling ◽  
C3 Photosynthesis ◽  
Leaf Level ◽  
Biochemical Level ◽  
Ancient Ecosystems ◽  
Palaeoenvironmental Changes

This paper presents an attempt to reconstruct potential changes in the photosynthetic rates of terrestrial C3 leaves over the past 120 Ma. The approach has been to couple palaeoatmospheric reconstructions of O 2 , CO 2 and temperature from geochemical modelling, and an independent estimate of ancient CO 2 changes from fossil porphyrins, with a mechanistic biochemical model of C3 photosynthesis. The model accounts for the effect of each of these palaeoenvironmental changes, at the biochemical level, to predict leaf photosynthesis and has been parametrized for a typical gymnosperm and angiosperm. The results indicate clear potential for increased photosynthetic C3 fixation in the warm Cretaceous for both angiosperms and gymnosperms, despite the increased O 2 content of the atmosphere prevailing at the time. Photosynthetic rates are then predicted to progressively decline into the Tertiary, as a result of global cooling. The model simulations also point towards some leaf-level ecophysiological explanations for the rise in angiosperm dominance and the concomitant decline in gymnosperms from the late Cretaceous onwards, at mid-latitudes, which have not been considered previously. This work provides a basis for scaling up to the canopy level to predict the primary productivity of ancient ecosystems and their possible feedback on atmospheric composition and climate.

scholarly journals Multi-model simulations of aerosol and ozone radiative forcing due to anthropogenic emission changes during the period 1990–2015

2017 ◽  
Vol 17 (4) ◽  
pp. 2709-2720 ◽  
Author(s):  
Gunnar Myhre ◽  
Wenche Aas ◽  
Ribu Cherian ◽  
William Collins ◽  
Greg Faluvegi ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Large Scale ◽  
Substantial Reduction ◽  
Atmospheric Composition ◽  
So2 Emissions ◽  
Emission Data ◽  
The Past ◽  
The Usa ◽  
Emission Changes ◽  
Global Mean

Abstract. Over the past few decades, the geographical distribution of emissions of substances that alter the atmospheric energy balance has changed due to economic growth and air pollution regulations. Here, we show the resulting changes to aerosol and ozone abundances and their radiative forcing using recently updated emission data for the period 1990–2015, as simulated by seven global atmospheric composition models. The models broadly reproduce large-scale changes in surface aerosol and ozone based on observations (e.g. −1 to −3 % yr−1 in aerosols over the USA and Europe). The global mean radiative forcing due to ozone and aerosol changes over the 1990–2015 period increased by +0.17 ± 0.08 W m−2, with approximately one-third due to ozone. This increase is more strongly positive than that reported in IPCC AR5. The main reasons for the increased positive radiative forcing of aerosols over this period are the substantial reduction of global mean SO2 emissions, which is stronger in the new emission inventory compared to that used in the IPCC analysis, and higher black carbon emissions.

scholarly journals Atmospheric composition and climate on the early Earth

2006 ◽  
Vol 361 (1474) ◽  
pp. 1733-1742 ◽  
Author(s):  
James F Kasting ◽  
M. Tazewell Howard
Keyword(s):  
Isotopic Composition ◽  
Isotope Fractionation ◽  
Atmospheric Composition ◽  
Early Earth ◽  
Geothermal Heat ◽  
Sulphur Isotope ◽  
Ocean Ridges ◽  
Early Atmosphere ◽  
Isotopic Records

Oxygen isotope data from ancient sedimentary rocks appear to suggest that the early Earth was significantly warmer than today, with estimates of surface temperatures between 45 and 85°C. We argue, following others, that this interpretation is incorrect—the same data can be explained via a change in isotopic composition of seawater with time. These changes in the isotopic composition could result from an increase in mean depth of the mid-ocean ridges caused by a decrease in geothermal heat flow with time. All this implies that the early Earth was warm, not hot. A more temperate early Earth is also easier to reconcile with the long-term glacial record. However, what triggered these early glaciations is still under debate. The Paleoproterozoic glaciations at approximately 2.4 Ga were probably caused by the rise of atmospheric O 2 and a concomitant decrease in greenhouse warming by CH 4 . Glaciation might have occurred in the Mid-Archaean as well, at approximately 2.9 Ga, perhaps as a consequence of anti-greenhouse cooling by hydrocarbon haze. Both glaciations are linked to decreases in the magnitude of mass-independent sulphur isotope fractionation in ancient rocks. Studying both the oxygen and sulphur isotopic records has thus proved useful in probing the composition of the early atmosphere.

scholarly journals Multi-model simulations of aerosol and ozone radiative forcing for the period 1990–2015

2016 ◽  
Author(s):  
Gunnar Myhre ◽  
Wenche Aas ◽  
Ribu Cherian ◽  
William Collins ◽  
Greg Faluvegi ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Large Scale ◽  
Emission Inventory ◽  
Substantial Reduction ◽  
Atmospheric Composition ◽  
So2 Emissions ◽  
Emission Data ◽  
Model Simulations ◽  
The Past ◽  
Global Mean

Abstract. Over the past decades, the geographical distribution of emissions of substances that alter the atmospheric energy balance has changed due to economic growth and pollution regulations. Here, we show the resulting changes to aerosol and ozone abundances and their radiative forcing, using recently updated emission data for the period 1990–2015, as simulated by seven global atmospheric composition models. The models broadly reproduce the large-scale changes in surface aerosol and ozone based on observations (e.g., −1 to −3 %/yr in aerosols over US and Europe). The global mean radiative forcing due to ozone and aerosols changes over the 1990–2015 period increased by about +0.2 W m−2, with approximately 1/3 due to ozone. This increase is stronger positive than reported in IPCC AR5. The main reason for the increased positive radiative forcing of aerosols over this period is the substantial reduction of global mean SO2 emissions which is stronger in the new emission inventory compared to the IPCC, and higher black carbon emissions.

scholarly journals Assessment of Tropospheric Concentrations of NO2 from the TROPOMI/Sentinel-5 Precursor for the Estimation of Long-Term Exposure to Surface NO2 over South Korea

2021 ◽  
Vol 13 (10) ◽  
pp. 1877
Author(s):  
Ukkyo Jeong ◽  
Hyunkee Hong
Keyword(s):  
South Korea ◽  
Spatial Resolution ◽  
Atmospheric Composition ◽  
Mixing Ratio ◽  
Mean Values ◽  
Mixing Ratios ◽  
Tropospheric No2 ◽  
Korean Ministry ◽  
Surface Mixing ◽  
Rural Sites

Since April 2018, the TROPOspheric Monitoring Instrument (TROPOMI) has provided data on tropospheric NO2 column concentrations (CTROPOMI) with unprecedented spatial resolution. This study aims to assess the capability of TROPOMI to acquire high spatial resolution data regarding surface NO2 mixing ratios. In general, the instrument effectively detected major and moderate sources of NO2 over South Korea with a clear weekday–weekend distinction. We compared the CTROPOMI with surface NO2 mixing ratio measurements from an extensive ground-based network over South Korea operated by the Korean Ministry of Environment (SKME; more than 570 sites), for 2019. Spatiotemporally collocated CTROPOMI and SKME showed a moderate correlation (correlation coefficient, r = 0.67), whereas their annual mean values at each site showed a higher correlation (r = 0.84). The CTROPOMI and SKME were well correlated around the Seoul metropolitan area, where significant amounts of NO2 prevailed throughout the year, whereas they showed lower correlation at rural sites. We converted the tropospheric NO2 from TROPOMI to the surface mixing ratio (STROPOMI) using the EAC4 (ECMWF Atmospheric Composition Reanalysis 4) profile shape, for quantitative comparison with the SKME. The estimated STROPOMI generally underestimated the in-situ value obtained, SKME (slope = 0.64), as reported in previous studies.

scholarly journals Widespread increase in dynamic imbalance in the Getz region of Antarctica from 1994 to 2018

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Heather L. Selley ◽  
Anna E. Hogg ◽  
Stephen Cornford ◽  
Pierre Dutrieux ◽  
Andrew Shepherd ◽  
...  
Keyword(s):  
Drainage Basin ◽  
Satellite Observations ◽  
Driving Mechanism ◽  
West Antarctica ◽  
Mean Sea Level ◽  
The Past ◽  
Global Mean Sea Level ◽  
Forcing Mechanisms ◽  
Global Mean ◽  
Term Response

AbstractThe Getz region of West Antarctica is losing ice at an increasing rate; however, the forcing mechanisms remain unclear. Here we use satellite observations and an ice sheet model to measure the change in ice speed and mass balance of the drainage basin over the last 25-years. Our results show a mean increase in speed of 23.8 % between 1994 and 2018, with three glaciers accelerating by over 44 %. Speedup across the Getz basin is linear, with speedup and thinning directly correlated confirming the presence of dynamic imbalance. Since 1994, 315 Gt of ice has been lost contributing 0.9 ± 0.6 mm global mean sea level, with increased loss since 2010 caused by a snowfall reduction. Overall, dynamic imbalance accounts for two thirds of the mass loss from this region of West Antarctica over the past 25-years, with a longer-term response to ocean forcing the likely driving mechanism.

scholarly journals One-Year Characterization and Reactivity of Isoprene and Its Impact on Surface Ozone Formation at A Suburban Site in Guangzhou, China

Atmosphere ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 201 ◽  
Author(s):  
Yu Zou ◽  
Xue Jiao Deng ◽  
Tao Deng ◽  
Chang Qin Yin ◽  
Fei Li
Keyword(s):  
Surface Ozone ◽  
Atmospheric Composition ◽  
Anthropogenic Factors ◽  
Mixing Ratio ◽  
Night Time ◽  
Subtropical Zone ◽  
Guangzhou City ◽  
Mixing Ratios ◽  
One Year ◽  
Suburban Site

Isoprene has a potentially large effect on ozone (O3) formation in the subtropical, highly polluted city of Guangzhou. Online measurements of isoprene in Guangzhou city are scarce; thus, isoprene levels were monitored for one year at the Guangzhou Panyu Atmospheric Composition Station (GPACS), a suburban site in Guangzhou, using an online gas chromatography-flame ionization detector (GC–FID) system to investigate the characterization and reactivity of isoprene and its effect on the O3 peak profile in different seasons. The results showed that the daily average mixing ratios of isoprene at GPACS were 0.40, 2.20, 1.40, and 0.13 mixing ratio by volume (ppbv) in spring, summer, autumn, and winter, respectively. These values were considerably higher than the mixing ratios of isoprene in the numerous other subtropical and temperate cities around the world. Furthermore, isoprene ranked first with regard to O3 formation potential (OFP) and propylene-equivalent mixing ratio among 56 measured non–methane hydrocarbons (NMHCs). The ratios of isoprene to cis-2-butene, an exhaust tracer, were determined to estimate the fractions of biogenic and anthropogenic emissions. The results revealed a much greater contribution from biogenic than anthropogenic factors during the daytime in all four seasons. In addition, night-time isoprene emissions were mostly associated with vehicles in winter, and the residual isoprene that remained after photochemical loss during the daytime also persisted into the night. The high levels of isoprene in summer and autumn may cause the strong and broad peaks of the O3 profile because of its association with the most favorable meteorological conditions (e.g., high temperature and intense solar radiation) and the highest OH mixing ratio, which could affect human health by exposing people to a high O3 mixing ratio for prolonged periods. The lower mixing ratios of isoprene resulted in a weak and sharp peak in the O3 profile in both spring and winter. The high level of isoprene in the subtropical zone could accentuate its large impact on atmospheric oxidant capacity and air quality in Guangzhou city.

scholarly journals Methane, oxygen, photosynthesis, rubisco and the regulation of the air through time

2008 ◽  
Vol 363 (1504) ◽  
pp. 2745-2754 ◽  
Author(s):  
Euan G Nisbet ◽  
R. Ellen R Nisbet
Keyword(s):  
Greenhouse Gas ◽  
Greenhouse Warming ◽  
Biological Productivity ◽  
Stable States ◽  
Mixing Ratios ◽  
The Past ◽  
Glacial Epoch ◽  
Air Control ◽  
Carbon Gases

Rubisco I's specificity, which today may be almost perfectly tuned to the task of cultivating the global garden, controlled the balance of carbon gases and O 2 in the Precambrian ocean and hence, by equilibration, in the air. Control of CO 2 and O 2 by rubisco I, coupled with CH 4 from methanogens, has for the past 2.9 Ga directed the global greenhouse warming, which maintains liquid oceans and sustains microbial ecology. Both rubisco compensation controls and the danger of greenhouse runaway (e.g. glaciation) put limits on biological productivity. Rubisco may sustain the air in either of two permissible stable states: either an anoxic system with greenhouse warming supported by both high methane mixing ratios as well as carbon dioxide, or an oxygen-rich system in which CO 2 largely fulfils the role of managing greenhouse gas, and in which methane is necessarily only a trace greenhouse gas, as is N 2 O. Transition from the anoxic to the oxic state risks glaciation. CO 2 build-up during a global snowball may be an essential precursor to a CO 2 -dominated greenhouse with high levels of atmospheric O 2 . Photosynthetic and greenhouse-controlling competitions between marine algae, cyanobacteria, and terrestrial C3 and C4 plants may collectively set the CO 2  : O 2 ratio of the modern atmosphere (last few million years ago in a mainly glacial epoch), maximizing the productivity close to rubisco compensation and glacial limits.

scholarly journals Changes in the strength and width of the Hadley Circulation since 1871

2012 ◽  
Vol 8 (4) ◽  
pp. 1169-1175 ◽  
Author(s):  
J. Liu ◽  
M. Song ◽  
Y. Hu ◽  
X. Ren
Keyword(s):  
20Th Century ◽  
Global Climate ◽  
Hadley Circulation ◽  
Recent Change ◽  
Early 20Th Century ◽  
Greenhouse Warming ◽  
Long Period ◽  
The Past ◽  
Period Oscillation

Abstract. Recent studies demonstrate that the Hadley Circulation has intensified and expanded for the past three decades, which has important implications for subtropical societies and may lead to profound changes in global climate. However, the robustness of this intensification and expansion that should be considered when interpreting long-term changes of the Hadley Circulation is still a matter of debate. It also remains largely unknown how the Hadley Circulation has evolved over longer periods. Here, we present long-term variability of the Hadley Circulation using the 20th Century Reanalysis. It shows a slight strengthening and widening of the Hadley Circulation since the late 1970s, which is not inconsistent with recent assessments. However, over centennial timescales (1871–2008), the Hadley Circulation shows a tendency towards a more intense and narrower state. More importantly, the width of the Hadley Circulation might have not yet completed a life-cycle since 1871. The strength and width of the Hadley Circulation during the late 19th to early 20th century show strong natural variability, exceeding variability that coincides with global warming in recent decades. These findings raise the question of whether the recent change in the Hadley Circulation is primarily attributed to greenhouse warming or to a long-period oscillation of the Hadley Circulation – substantially longer than that observed in previous studies.

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