The condensation trail emitted by jet aircraft exhaust are called c...
Contrails can have either a cooling or a warming effect:
- They ...
Andrew Gettelman et. al performed a similar studied but in this cas...
Aircraft might have climate impacts through both $CO_2$ and non-$CO...
The warming effects of contrails differ during the day and during t...
T
he potential of condensation trails
(contrails) from jet aircraft to affect
regional-scale surface temperatures has
been debated for years
1–3
, but was difficult
to verify until an opportunity arose as a
result of the three-day grounding of all
commercial aircraft in the United States in
the aftermath of the terrorist attacks on 11
September 2001. Here we show that there
was an anomalous increase in the average
diurnal temperature range (that is, the dif-
ference between the daytime maximum and
night-time minimum temperatures) for the
period 11–14 September 2001. Because per-
sisting contrails can reduce the transfer of
both incoming solar and outgoing infrared
radiation
4,5
and so reduce the daily tempera-
ture range, we attribute at least a portion of
this anomaly to the absence of contrails
over this period.
We a na lysed m ax im um a nd m in im um
temperature data
6
from about 4,000 weather
stations throughout the conterminous Unit-
ed States (the 48 states not including Alaska
and Hawaii) for the period 1971–2000,
and compared these to the conditions that
prevailed during the three-day aircraft-
grounding period. All sites were inspected
for data quality and adjusted for the time
of observation.
Because the grounding period com-
menced after the minimum temperatures
had been reached on the morning of 11
September and ended before maximum
temperatures were attained on 14 Septem-
ber (at noon, Eastern Standard Time), we
staggered the calculation of the average
diurnal temperature range (DTR) across
adjacent days (for example, 11 September
maxima minus 12 September minima). We
repeated this procedure for the three-day
periods immediately before and after the
grounding period, and also for the same
periods (8–11, 11–14 and 14–17 September)
for each year from 1971 to 2000.
DTRs for 11–14 September 2001 mea-
sured at stations across the United States
show an increase of about 1.1 !C over
normal 1971–2000 values (Fig. 1). This is in
contrast to the adjacent three-day periods,
when DTR values were near or below the
mean (Fig. 1). DTR departures for the
grounding period are, on average, 1.8 !C
greater than DTR departures for the two
adjacent three-day periods.
This increase in DTR is larger than any
during the 11–14 September period for the
previous 30 years, and is the only increase
greater than 2 standard deviations away
from the mean DTR (s.d., 0.85 !C). More-
over, the 11–14 September increase in DTR
was more than twice the national average for
regions of the United States where contrail
coverage has previously been reported to
be most abundant (such as the midwest,
northeast and northwest regions)
7
.
Day-to-day changes in synoptic atmos-
pheric conditions can affect regional DTRs
8
.
In particular, a lack of cloud cover helps to
increase the maximum (and reduce the
minimum) temperature. Maps of the daily
average outgoing long-wave radiation
(OLR)
9,10
— a proxy for optically thick
clouds — show reduced cloudiness (that is,
larger OLR) over the eastern half of the
United States on 11 September, but more
cloud (smaller OLR) over parts of the west.
Cloud cover subsequently decreased in the
west and increased over much of the eastern
half of the country during the next two
days, producing predominantly negative
three-day OLR changes in the east and
positive values in parts of the west.
Our findings indicate that the diurnal
temperature range averaged across the United
States was increased during the aircraft-
grounding period, despite large variations in
the amount of cloud associated with mobile
weather systems (Fig. 2). We argue that the
absence of contrails was responsible for
the difference between a period of above-
normal but unremarkable DTR and the
anomalous conditions that were recorded.
David J. Travis*, Andrew M. Carleton†,
Ryan G. Lauritsen*
*Department of Geography and Geology,
University of Wisconsin–Whitewater, Whitewater,
Wisconsin 53190, USA
e-mail: travisd@.uww.edu
†Department of Geography, Pennsylvania State
University, University Park,
Pennsylvania 16801, USA
1. Changnon, S. A. J. Appl. Meteorol. 20, 496–508 (1981).
2. Travis, D. J. & Changnon, S. A. J. Weather Modification 29,
74–83 (1997).
3. Sassen, K. Bull. Am. Meteorol. Soc. 78, 1885–1903 (1997).
4. Duda, D. P., Minnis, P. & Nguyen, L. J. Geophys. Res. 106,
4927–4937 (2001).
5. Meerkotter, R. et al. Ann. Geophys. 17, 1080–1094 (1999).
6. National Oceanic and Atmospheric Administration.
TD3200/3210 Data Set for 1971–2001 (Natl Climate Data
Center, Asheville, North Carolina, 2001).
7. DeGrand, J. Q., Carleton, A. M., Travis, D. J. & Lamb, P. J. Appl.
Meteorol. 39, 1434–1459 (2000).
8. Karl, T. R. et al. Bull Am. Meteorol. Soc. 74, 1007–1023 (1993).
9. Liebmann, B. & Smith, C. A. Bull Am. Meteorol. Soc. 77,
1275–1277 (1996).
10.http://www.cdc.noaa.gov (NOAA-CIRES Climate Diagnostics
Center, Boulder, Colorado, USA).
Competing financial interests:declared none.
brief communications
NATURE
|
VOL 418
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8 AUGUST 2002
|
www.nature.com/nature 601
Contrails reduce daily temperature range
A brief interval when the skies were clear of jets unmasked an effect on climate.
NOAA SATELLITE ACTIVE ARCHIVE
Figure 1 Departure of average diurnal temperature ranges (DTRs)
from the normal values derived from 1971–2000 climatology
data for the indicated three-day periods in September 2001.
These periods included the three days before the terrorist attacks
of 11 September; the three days immediately afterwards, when
aircraft were grounded and there were therefore no contrails; and
the subsequent three days.
1.5
1
0.5
0
–0.5
–1
Change in DTR (°C)
8–11 Sept.
11–14 Sept.
14–17 Sept.
Figure 2 Flight lines: jet contrails can clearly be seen as thin
streaks in this satellite image of the southwestern United States.
frogs from the mountains of Papua New
Guinea. As the offspring jump off at
different points, they may benefit from
reduced competition for food, lower
predation pressure and fewer oppor-
tunities for inbreeding between froglets,
which may explain why this unusual form
of parental care evolved.
I quantified the parental care behaviour
of several species of microhylid frog at
the Crater Mountain Biological Research
Station, Chimbu Province, Papua New
Guinea (6° 43" S, 145° 05" E), which is
located on the largest tropical island in
Animal behaviour
Male parenting of
New Guinea froglets
M
ale parental care is exceptionally
rare in nature, although one of
the most fascinating aspects of
New Guinea’s biodiversity is the evolution
of male care in the frog family
Microhylidae
1
. Here I report a new mode
of parental care: transport of froglets
by the male parent, which was recently
discovered in two species of microhylid
Aircraft might have climate impacts through both $CO_2$ and non-$CO_2$ contributions. Global aviation contributes 3.5% to total anthropogenic [radiative forcing](https://en.wikipedia.org/wiki/Radiative_forcing), but non-$CO_2$ effects comprise about 2/3 of the net radiative forcing. The largest single contribution to aviation radiative forcing is contrails and contrail cirrus, with an estimated 2018 impact of 0.06 W m−2 (60 mW m−2) with high uncertainty.
Contrails can have either a cooling or a warming effect:
- They can cause warming by trapping long-wave (infrared) radiation from the Earth, and
- They can cause cooling by reflecting short-wave (visible and ultraviolet) solar radiation back into space.
Overall, however, clouds caused by air travel emissions have a significant net warming effect integrating over space and time ([Lee 2018](https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/813342/non-CO2-effects-report.pdf)) - the net effect depends on the cirrus microphysical and radiative properties, and the variation in shortwave radiation.
Andrew Gettelman et. al performed a similar studied but in this case measuring the impact of [COVID-19-induced contrail changes](https://acp.copernicus.org/articles/21/9405/2021/).
The warming effects of contrails differ during the day and during the night. During the day, contrails trap infrared radiation (a warming effect) and reflect solar radiation (a cooling effect). At night, they only trap infrared radiation and there is no cooling effect.
The condensation trail emitted by jet aircraft exhaust are called contrails. Contrails are formed by soot aerosol particles and water vapor emissions, that allow background water vapor to condense on the soot aerosol particles to form ice crystals. Whether contrails form depends on the flight altitude as well as on the temperature and humidity of the atmosphere. About 10 to 20% of all flights cause contrails, and they are short-lived.
Contrails rapidly dissipate or spread horizontally into an extensive thin cirrus layer. How long a contrail remains intact depends on the humidity structure and winds of the upper troposphere. If the atmosphere is near saturation the contrail may exist for some time. On the other hand, if the atmosphere is dry then as the contrail mixes with the environment it dissipates.
