scholarly journals Effect of contrail overlap on radiative impact attributable to aviation contrails

2020 ◽  
Author(s):  
Inés Sanz-Morère ◽  
Sebastian D. Eastham ◽  
Florian Allroggen ◽  
Raymond L. Speth ◽  
Steven R. H. Barrett
Keyword(s):  
North Atlantic ◽  
Airline Industry ◽  
Radiative Forcing ◽  
Geographic Location ◽  
Longwave Radiation ◽  
Climate Impact ◽  
Climate Impacts ◽  
The North ◽  
Radiative Impact ◽  
Total Impact

Abstract. Condensation trails (“contrails”) which form behind aircraft are estimated to cause on the order of 50 % of the total climate impact of aviation, matching the total impact of all accumulated aviation-attributable CO2. The climate impacts of these contrails are highly uncertain, in part due to the poorly-understood effect of overlap between contrails and other cloud layers. With the airline industry projected to grow by approximately 4.5 % each year over the next 20 years, instances of contrail overlap are expected to increase, including any potential mitigating or amplifying effects on contrail-attributable radiative forcing. However, the impacts of cloud-contrail overlaps are not well understood, and the effect of contrail-contrail overlap has never been quantified. In this study we develop and apply a new model of contrail radiative forcing which explicitly accounts for overlap between cloud layers. Cloud-contrail overlap is found to be responsible for 93 % of net radiative forcing attributable to 2015 contrails. We also find significant variation in the sensitivity of contrail radiative forcing to cloud cover with respect to geographic location. Clouds significantly increase warming at high latitudes and over sea, transforming cooling contrails into warming ones in the North-Atlantic corridor. Based on the same data, our results indicate that disregarding overlap between a given pair of contrail layers can result in longwave and shortwave radiative forcing being overestimated by up to 16 % and 25 % respectively, with the highest bias observed at high optical depths (> 0.4) and high solar zenith angles (> 75°). When applied to estimated global contrail coverage data for 2015, contrail-contrail overlap reduces both the longwave and shortwave forcing by ~ 2 % relative to calculations which ignore overlap. The effect is greater for longwave radiation, resulting in a 3 % net reduction in the estimated RF when overlap is correctly accounted for. This suggests that contrail-contrail overlap effects can likely be neglected in estimates of the current-day environmental impacts of aviation. However, the effect of contrail-contrail overlap is likely to increase in the future as the airline industry extends into new regions, intensifies in existing regions, and invests in higher-efficiency engines which are thought to promote contrail formation.

scholarly journals Impacts of multi-layer overlap on contrail radiative forcing

2021 ◽  
Vol 21 (3) ◽  
pp. 1649-1681
Author(s):  
Inés Sanz-Morère ◽  
Sebastian D. Eastham ◽  
Florian Allroggen ◽  
Raymond L. Speth ◽  
Steven R. H. Barrett
Keyword(s):  
North Atlantic ◽  
Airline Industry ◽  
Radiative Forcing ◽  
Geographic Location ◽  
Longwave Radiation ◽  
Climate Impacts ◽  
Climate Forcing ◽  
The North ◽  
The North Atlantic ◽  
Total Impact

Abstract. Condensation trails (“contrails”) which form behind aircraft are estimated to cause on the order of 50 % of the total climate forcing of aviation, matching the total impact of all accumulated aviation-attributable CO2. The climate impacts of these contrails are highly uncertain, in part due to the effect of overlap between contrails and other cloud layers. Although literature estimates suggest that overlap could change even the sign of contrail radiative forcing (RF), the impacts of cloud–contrail overlaps are not well understood, and the effect of contrail–contrail overlap has never been quantified. In this study we develop and apply a new model of contrail radiative forcing which explicitly accounts for overlap between cloud layers. Assuming maximum possible overlap to provide an upper bound on impacts, cloud–contrail overlap is found to reduce the shortwave-cooling effect attributable to aviation by 66 % while reducing the longwave-warming effect by only 37 %. Therefore, on average in 2015, cloud–contrail overlap increased the net radiative forcing from contrails. We also quantify the sensitivity of contrail radiative forcing to cloud cover with respect to geographic location. Clouds significantly increase warming at high latitudes and over sea, transforming cooling contrails into warming ones in the North Atlantic corridor. Based on the same data, our results indicate that disregarding overlap between a given pair of contrail layers can result in longwave and shortwave radiative forcing being overestimated by up to 16 % and 25 %, respectively, with the highest bias observed at high optical depths (> 0.4) and high solar zenith angles (> 75∘). When applied to estimated global contrail coverage data for 2015, contrail–contrail overlap reduces both the longwave and shortwave forcing by ∼ 2 % relative to calculations which ignore overlap. The effect is greater for longwave radiation, resulting in a 3 % net reduction in the estimated RF when overlap is correctly accounted for. This suggests that contrail–contrail overlap radiative effects can likely be neglected in estimates of the current-day environmental impacts of aviation. However, the effect of contrail–contrail overlap may increase in the future as the airline industry grows into new regions.

scholarly journals NAO predictability from external forcing in the late 20th century

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Jeremy M. Klavans ◽  
Mark A. Cane ◽  
Amy C. Clement ◽  
Lisa N. Murphy
Keyword(s):  
North Atlantic ◽  
Radiative Forcing ◽  
Climate Models ◽  
North Atlantic Ocean ◽  
Signal To Noise Ratio ◽  
Prediction System ◽  
Signal To Noise ◽  
Late 20Th Century ◽  
The North ◽  
Predictive Skill

AbstractThe North Atlantic Oscillation (NAO) is predictable in climate models at near-decadal timescales. Predictive skill derives from ocean initialization, which can capture variability internal to the climate system, and from external radiative forcing. Herein, we show that predictive skill for the NAO in a very large uninitialized multi-model ensemble is commensurate with previously reported skill from a state-of-the-art initialized prediction system. The uninitialized ensemble and initialized prediction system produce similar levels of skill for northern European precipitation and North Atlantic SSTs. Identifying these predictable components becomes possible in a very large ensemble, confirming the erroneously low signal-to-noise ratio previously identified in both initialized and uninitialized climate models. Though the results here imply that external radiative forcing is a major source of predictive skill for the NAO, they also indicate that ocean initialization may be important for particular NAO events (the mid-1990s strong positive NAO), and, as previously suggested, in certain ocean regions such as the subpolar North Atlantic ocean. Overall, we suggest that improving climate models’ response to external radiative forcing may help resolve the known signal-to-noise error in climate models.

scholarly journals Climate impact on the development of Pre-Classic Maya civilisation

2018 ◽  
Vol 14 (8) ◽  
pp. 1253-1273 ◽  
Author(s):  
Kees Nooren ◽  
Wim Z. Hoek ◽  
Brian J. Dermody ◽  
Didier Galop ◽  
Sarah Metcalfe ◽  
...  
Keyword(s):  
North Atlantic ◽  
Agricultural Intensification ◽  
Climatic Variability ◽  
Regional Scale ◽  
Climate Impact ◽  
Classic Period ◽  
Beach Ridge ◽  
Maya Lowlands ◽  
The North ◽  
The Impact

Abstract. The impact of climate change on the development and disintegration of Maya civilisation has long been debated. The lack of agreement among existing palaeoclimatic records from the region has prevented a detailed understanding of regional-scale climatic variability, its climatic forcing mechanisms and its impact on the ancient Maya. We present two new palaeo-precipitation records for the central Maya lowlands, spanning the Pre-Classic period (1800 BCE–250 CE), a key epoch in the development of Maya civilisation. A beach ridge elevation record from world's largest late Holocene beach ridge plain provides a regional picture, while Lake Tuspan's diatom record is indicative of precipitation changes at a local scale. We identify centennial-scale variability in palaeo-precipitation that significantly correlates with the North Atlantic δ14C atmospheric record, with a comparable periodicity of approximately 500 years, indicating an important role of North Atlantic atmospheric–oceanic forcing on precipitation in the central Maya lowlands. Our results show that the Early Pre-Classic period was characterised by relatively dry conditions, shifting to wetter conditions during the Middle Pre-Classic period, around the well-known 850 BCE (2.8 ka) event. We propose that this wet period may have been unfavourable for agricultural intensification in the central Maya lowlands, explaining the relatively delayed development of Maya civilisation in this area. A return to relatively drier conditions during the Late Pre-Classic period coincides with rapid agricultural intensification in the region and the establishment of major cities.

scholarly journals Climate impacts on multidecadal <i>p</i>CO<sub>2</sub> variability in the North Atlantic: 1948–2009

2015 ◽  
Vol 12 (17) ◽  
pp. 15223-15244
Author(s):  
M. L. Breeden ◽  
G. A. McKinley
Keyword(s):  
North Atlantic ◽  
Large Scale ◽  
Dissolved Inorganic Carbon ◽  
Atlantic Multidecadal Oscillation ◽  
Climate Impacts ◽  
Co2 Uptake ◽  
Subpolar Gyre ◽  
The North ◽  
The North Atlantic

Abstract. The North Atlantic is the most intense region of ocean CO2 uptake. Here, we investigate multidecadal timescale variability of the partial pressure CO2 (pCO2) that is due to the natural carbon cycle using a regional model forced with realistic climate and pre-industrial atmospheric pCO2 for 1948–2009. Large-scale patterns of natural pCO2 variability are primarily associated with basin-averaged sea surface temperature (SST) that, in turn, is composed of two parts: the Atlantic Multidecadal Oscillation (AMO) and a long-term positive SST trend. The North Atlantic Oscillation (NAO) drives a secondary mode of variability. For the primary mode, positive AMO and the SST trend modify pCO2 with different mechanisms and spatial patterns. Warming with the positive AMO increases subpolar gyre pCO2, but there is also a significant reduction of dissolved inorganic carbon (DIC) due primarily to reduced vertical mixing. The net impact of positive AMO is to reduce pCO2 in the subpolar gyre. Through direct impacts on SST, the net impacts of positive AMO is to increase pCO2 in the subtropical gyre. From 1980 to present, long-term SST warming has amplified AMO impacts on pCO2.

scholarly journals Instantaneous longwave radiative impact of ozone: an application on IASI/MetOp observations

2015 ◽  
Vol 15 (15) ◽  
pp. 21177-21218
Author(s):  
S. Doniki ◽  
D. Hurtmans ◽  
L. Clarisse ◽  
C. Clerbaux ◽  
H. M. Worden ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Climate Model ◽  
Longwave Radiation ◽  
Polar Regions ◽  
Direct Integration ◽  
Direct Integration Method ◽  
Radiative Impact ◽  
Ozone Variation ◽  
Atmospheric Sounding ◽  
Stratospheric Intrusions

Abstract. Ozone is an important greenhouse gas in terms of anthropogenic radiative forcing (RF). RF calculations for ozone were until recently entirely model based and significant discrepancies were reported due to different model characteristics. However, new instantaneous radiative kernels (IRKs) calculated from hyperspectral thermal IR satellites have been able to help adjudicate between different climate model RF calculations. IRKs are defined as the sensitivity of the outgoing longwave radiation (OLR) flux with respect to the ozone vertical distribution in the full 9.6 μm band. Previous methods applied to measurements from the Tropospheric Emission Spectrometer (TES) on Aura, rely on an anisotropy approximation for the angular integration. In this paper, we present a more accurate but more computationally expensive method to calculate these kernels. The method of direct integration is based on similar principles with the anisotropy approximation, but deals more precisely with the integration of the Jacobians. We describe both methods and highlight their differences with respect to the IRKs and the ozone longwave radiative effect (LWRE), i.e. the radiative impact in OLR due to absorption by ozone, for both tropospheric and total columns, from measurements of the Infrared Atmospheric Sounding Interferometer (IASI) onboard MetOp-A. Biases between the two methods vary from −25 to +20 % for the LWRE, depending on the viewing angle. These biases point to the inadequacy of the anisotropy method, especially at nadir, suggesting that the TES derived LWRE are biased low by around 25 % and that chemistry-climate model OLR biases with respect to TES are underestimated. In this paper we also exploit the sampling performance of IASI to obtain first daily global distributions of the LWRE, for 12 days (the 15th of each month) in 2011, calculated with the direct integration method. We show that the temporal variation of global and latitudinal averages of the LWRE shows patterns which are controlled by changes in the surface temperature and ozone variation due to specific processes, such as the ozone hole in the Polar regions and stratospheric intrusions into the troposphere.

Evolving Relative Importance of the Southern Ocean and North Atlantic in Anthropogenic Ocean Heat Uptake

2018 ◽  
Vol 31 (18) ◽  
pp. 7459-7479 ◽  
Author(s):  
Jia-Rui Shi ◽  
Shang-Ping Xie ◽  
Lynne D. Talley
Keyword(s):  
Southern Ocean ◽  
North Atlantic ◽  
Radiative Forcing ◽  
Meridional Overturning Circulation ◽  
Anthropogenic Heat ◽  
Anthropogenic Aerosols ◽  
Ocean Heat Uptake ◽  
The North ◽  
Heat Uptake ◽  
The North Atlantic

Ocean uptake of anthropogenic heat over the past 15 years has mostly occurred in the Southern Ocean, based on Argo float observations. This agrees with historical simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5), where the Southern Ocean (south of 30°S) accounts for 72% ± 28% of global heat uptake, while the contribution from the North Atlantic north of 30°N is only 6%. Aerosols preferentially cool the Northern Hemisphere, and the effect on surface heat flux over the subpolar North Atlantic opposes the greenhouse gas (GHG) effect in nearly equal magnitude. This heat uptake compensation is associated with weakening (strengthening) of the Atlantic meridional overturning circulation (AMOC) in response to GHG (aerosol) radiative forcing. Aerosols are projected to decline in the near future, reinforcing the greenhouse effect on the North Atlantic heat uptake. As a result, the Southern Ocean, which will continue to take up anthropogenic heat largely through the mean upwelling of water from depth, will be joined by increased relative contribution from the North Atlantic because of substantial AMOC slowdown in the twenty-first century. In the RCP8.5 scenario, the percentage contribution to global uptake is projected to decrease to 48% ± 8% in the Southern Ocean and increase to 26% ± 6% in the northern North Atlantic. Despite the large uncertainty in the magnitude of projected aerosol forcing, our results suggest that anthropogenic aerosols, given their geographic distributions and temporal trajectories, strongly influence the high-latitude ocean heat uptake and interhemispheric asymmetry through AMOC change.

Why Is There an Early Spring Cooling Shift Downstream of the Tibetan Plateau?

2005 ◽  
Vol 18 (22) ◽  
pp. 4660-4668 ◽  
Author(s):  
Jian Li ◽  
Rucong Yu ◽  
Tianjun Zhou ◽  
Bin Wang
Keyword(s):  
Tibetan Plateau ◽  
North Africa ◽  
North Atlantic ◽  
Radiative Forcing ◽  
Temperature Shift ◽  
Early Spring ◽  
Climate Feedback ◽  
The Tibetan Plateau ◽  
The North ◽  
The North Atlantic

Abstract The temperature shift over the eastern flank of the Tibetan Plateau is examined using the last 50 yr of Chinese surface station observations. It was found that a strong cooling shift occurs in early spring (March and April) and late summer (July, August, and September) in contrast to the warming shift in other seasons. The cause of the March–April (MA) cooling is investigated in this study. The MA cooling shift on the lee side of the Tibetan Plateau is found to be not a local phenomenon, but rather it is associated with an eastward extension of a cooling signal originating from North Africa that is related to the North Atlantic Oscillation (NAO) in the previous winter. The midtropospheric westerlies over the North Atlantic and North Africa tend to intensify during positive NAO phases. The enhanced westerlies, after passing over the Tibetan Plateau, result in strengthened ascending motion against the lee side of the plateau, which favors the formation of midlevel stratiform clouds. The increased amount of stratus clouds induces a negative net cloud–radiative forcing, which thereby cools the surface air and triggers a positive cloud–temperature feedback. In this way, the cooling signal from the upstream could “jump” over the Tibetan Plateau and leave a footprint on its lee side. The continental stratiform cloud–climate feedback plays a significant role in the amplification of the cooling shift downstream of the Tibetan Plateau.

The Application of Advanced Systems – An Airline Perspective

1994 ◽  
Vol 47 (2) ◽  
pp. 177-180
Author(s):  
K. Reid
Keyword(s):  
North Atlantic ◽  
Airline Industry ◽  
Traffic Management ◽  
Air Traffic Management ◽  
Civil Aviation ◽  
Peak Time ◽  
The North ◽  
Movement Study ◽  
Track Area ◽  
Navigation Equipment

The achievement of the goals of the International Civil Aviation Organization (ICAO) Future Air Navigation System (FANS) is essential for the continued development of the airline industry. A recently completed movement study for the North Atlantic Track area forecast that the previously anticipated aircraft movements for 2010 would now be achieved by 1999. Peak time capacity growth for the region is now reliant on the introduction of Reduced Vertical Separation Minima (RVSM) scheduled for January 1997. Similarly, Europe had an all-too-evident capacity problem though some alleviation should follow from the introduction of precision area navigation (PRNAV) routeings in early 1998. However, despite the introduction of these developments, the restrictions on flow rates imposed by capacity variations in adjacent areas will remain. Quite obviously, an enhanced and fully capable Air Traffic Management (ATM) environment is required to solve many of the problems that commonly exist today. Nevertheless, more could be achieved through the application and exploitation of advanced navigation equipment such as the aircraft Flight Management Computer System (FMS) that is in widespread use today – a theme that will be returned to later in the paper.

Infrared radiative forcing of a Saharan dust plume in the North Atlantic

1998 ◽  
Vol 29 ◽  
pp. S1301-S1302 ◽  
Author(s):  
P. Chazette ◽  
J. Pelon ◽  
I. Carrasco ◽  
V. Trouillet ◽  
F. Dulac
Keyword(s):  
North Atlantic ◽  
Radiative Forcing ◽  
Saharan Dust ◽  
The North ◽  
The North Atlantic

scholarly journals Modelling global-scale climate impacts of the late Miocene Messinian Salinity Crisis

2013 ◽  
Vol 9 (4) ◽  
pp. 4807-4853 ◽  
Author(s):  
R. F. Ivanovic ◽  
P. J. Valdes ◽  
R. Flecker ◽  
M. Gutjahr
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Late Miocene ◽  
General Circulation ◽  
North Atlantic Ocean ◽  
Global Scale ◽  
Climate Impacts ◽  
Meridional Overturning Circulation ◽  
Messinian Salinity Crisis ◽  
The North

Abstract. Late Miocene tectonic changes in Mediterranean–Atlantic connectivity and climatic changes caused Mediterranean salinity to fluctuate dramatically, including a ten-fold increase and near-freshening. Recent proxy- and model-based evidence suggests that at times during this Messinian Salinity Crisis (MSC, 5.96–5.33 Ma), highly-saline and highly-fresh Mediterranean water flowed into the North Atlantic Ocean, whilst at others, no Mediterranean Outflow Water (MOW) reached the Atlantic. By running extreme, sensitivity-type experiments with a fully-coupled ocean–atmosphere general circulation model, we investigate the potential of these various MSC MOW scenarios to impact global-scale climate. The simulations suggest that MOW had a greater influence on North Atlantic Ocean circulation and climate than it does today. We also find that depending on the presence, strength and salinity of MOW, the MSC could have been capable of cooling mid-high northern latitudes by more than 1.2 °C, with the greatest cooling taking place in the Labrador, Greenland–Iceland–Norwegian and Barents Seas. With hypersaline-MOW, a component of North Atlantic Deep Water formation shifts to the Mediterranean, strengthening the Atlantic Meridional Overturning Circulation (AMOC) south of 35° N by 3–7 Sv. With hyposaline-MOW, AMOC completely shuts down, inducing a bipolar climate anomaly with strong cooling in the North (up to −10.5 °C) and weaker warming in the South (up to +2.5 °C). These simulations identify key target regions and climate variables for future proxy-reconstructions to provide the best and most robust test cases for (a) assessing Messinian model performance, (b) evaluating Mediterranean–Atlantic connectivity during the MSC and (c) establishing whether or not the MSC could ever have affected global-scale climate.

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