Abstract. In this paper, we present the global fingerprint of recent changes in
middle–upper stratosphere (MUSt; <25 hPa) ozone (O3) in
comparison with lower stratosphere (LSt; 150–25 hPa) O3 derived
from the first 10 years of the IASI/Metop-A satellite measurements (January 2008–December 2017). The IASI instrument provides vertically resolved
O3 profiles with very high spatial and temporal (twice daily)
samplings, allowing O3 changes to be monitored in these two regions of the
stratosphere. By applying multivariate regression models with adapted
geophysical proxies on daily mean O3 time series, we discriminate
anthropogenic trends from various modes of natural variability, such as the
El Niño–Southern Oscillation (ENSO). The representativeness of the
O3 response to its natural drivers is first examined. One important
finding relies on a pronounced contrast between a positive LSt O3
response to ENSO in the extratropics and a negative one in the tropics,
with a delay of 3 months, which supports a stratospheric pathway for the
ENSO influence on lower stratospheric and tropospheric O3. In terms of
trends, we find an unequivocal O3 recovery from the available period of
measurements in winter–spring at middle to high latitudes for the two
stratospheric layers sounded by IASI (>∼35∘ N–S in the MUSt and >∼45∘ S in the LSt) as well as in the total columns at southern latitudes
(>∼45∘ S) where the increase reaches
its maximum. These results confirm the effectiveness of the Montreal
Protocol and its amendments and represent the first detection of a
significant recovery of O3 concurrently in the lower, in the middle–upper
stratosphere and in the total column from one single satellite dataset. A
significant decline in O3 at northern mid-latitudes in the LSt is also
detected, especially in winter–spring of the Northern Hemisphere. Given
counteracting trends in the LSt and MUSt at these latitudes, the decline is not
categorical in total O3. When freezing the regression coefficients
determined for each natural driver over the whole IASI period but adjusting
a trend, we calculate a significant speeding up in the O3 response to
the decline of O3-depleting substances (ODSs) in the total column, in
the LSt and, to a lesser extent, in the MUSt, at high southern latitudes
over the year. Results also show a small significant acceleration of the
O3 decline at northern mid-latitudes in the LSt and in the total column
over the last few years. That, specifically, needs urgent investigation to
identify its exact origin and apprehend its impact on climate change.
Additional years of IASI measurements would, however, be required to confirm
the O3 change rates observed in the stratospheric layers over the last few
years.
Bushmeat biogeochemistry: hunting tropical mammals alters ecosystem phosphorus budgets