The Scientific Foundation of the Montreal Protocol

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The scientific foundation of the Montreal Protocol: past, present, and future Presentations by the panelists • Past and present changes in atmospheric composition and the ozone layer Dr. Vitali Fioletov, Environment and Climate Change Canada • Effects of future changes in atmospheric composition on the ozone layer Dr. Nathan Gillett, Environment and Climate Change Canada • Effects on climate from ozone depletion and recovery Dr. Amanda Maycock, Leeds University, UK • HFC and climate projection by the Kigali amendment Dr. Guus Velders, Utrecht University and RIVM, The Netherlands • Monitoring ozone - more important than ever Dr. Anne Thompson, NASA Goddard, USA Moderator: Dr. Mona Nemer, Government of Canada

Past and present changes in atmospheric composition and the ozone layer Vitali Fioletov, Environment and Climate Change Canada 3 Ozone in the stratosphere

The ozoneOzone distributionMixing Ratio (mixing(PPM) ratio) The ozone transport 60 10

50 8 7

40 5

30 3 2 Height (km) 1 20

10 The main source is here

0 90S 60S 30S 0 30N 60N 90N Latitude Ozone is largely produced in the Ozone over middle and high latitudes tropical middle stratosphere is mainly transported from the tropics 4 Time series of the ozone layer thickness Annual mean values Monthly mean values Northern Midlatitudes Total ozone time The Arctic, March Pre-1980 level series show a decline Pre-1980 level (except for the tropics) from the benchmark pre-1980 level, but also a large year-to- Total Ozone (DU) Total year variability Pre-1980 level The Antarctic, October Southern Midlatitudes

Pre-1980 level Total Ozone (DU) Total

Dobson Unit (DU) is a measure of the ozone

Total Ozone (DU) Total layer thickness. Different colors represent six 1970 1980 1990 2000 2010 1970 1980 1990 2000 2010 different data sets. 1970 1980 1990 2000 2010

From Weber et al., BAMS State of Climate, 2017 The Equivalent Effective Stratospheric Chlorine 5

Total ozone is influenced by annual The EESC curve cycle, solar cycle variations, and variations in tropical stratospheric wind and volcanic aerosol

The Equivalent Effective Stratospheric Chlorine (EESC) is often used as a measure of ozone depleting substances (ODSs) to quantify ozone depletion

EESC is the sum of chlorine (Cl) and bromine (Br) in the stratosphere derived from ODS tropospheric abundances, weighted to reflect their ability to deplete stratospheric ozone (From Newman et al., 2007). 6 Does the Montreal Protocol work?

The EESC curve Upper stratosphere Total ozone, 60°S-60°N Northern midlatitudes 350 Total ozone, Antarctica

HALLEY SYOWA 300 AMUNDSEN-SCOTT FARADAY / VERNADSKY EESC 250

200

150

Min. Total Ozone (DU) 100 Ozone anomaly Ozone anomaly (DU) 50 1960 1970 1980 1990 2000 2010 2020

Total ozone anomalies adjusted Minimum daily total ozone values Annual mean ozone anomalies at for the natural variability (updated (DU) in September-October at 40 km (from Chipperfield et al., Nature, from Fioletov, 2008) four sites 2017)

Since EESC is a proxy for ozone depletion, various characteristics of ozone depletion should follow the shape of the EESC curve 7 60°N-60°S partial column ozone Ozone trends Upper stratosphere (32-48 km)

Strong ozone declines were observed between 1979 and 1996, largest near the poles. Total ozone trends from 1997 to 2016 as a function of latitude Middle stratosphere (24-32 km) are mostly not significant

There is almost no total ozone change over northern midlatitudes after 1997 Ozone deviations (DU) Lower stratosphere (15-24 km) Since 1997, ozone concentration has increased in the upper stratosphere, but not in the lower stratosphere

From Ball et al., ACP 2017 Effects of future changes in atmospheric composition on the ozone layer Nathan Gillett, Environment and Climate Change Canada Future changes in Ozone Depleting Substances • Actions taken under the Montreal Protocol have led to decreases in the atmospheric concentration of ozone depleting substances. • Stratospheric chlorine (EESC) is expected to return to its 1980 values around 2050 for the midlatitudes and around 2075 for the Antarctic. Long-term changes in EESC due to the Montreal Protocol and its amendments and adjustments. EESC is the sum of chlorine (Cl) and bromine (Br) in the stratosphere derived from tropospheric abundances of Ozone Depleting Substances, weighted to reflect their ability to deplete stratospheric ozone (WMO, 2010).

Future changes in greenhouse gases and their effects on ozone • Ozone-depleting substances (ODSs) were the dominant driver of global ozone decline in the late 20th century. • As controlled ODS concentrations decline, carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) will strongly influence ozone evolution in the latter part of the 21st century.

• Overall N2O increases will tend to decrease ozone, while increasing Simulated global/annual averaged total ozone CH4 and CO2 will tend to increase ozone. response to IPCC SRES A1B changes in CO2 (red line), CH4 (brown line), N2O (green line), and ODSs (blue line), and combined effects (black) compared to observations (magenta crosses) (WMO, 2014). Projections of global stratospheric ozone • Total column ozone will recover toward the 1980 level over most of the globe under full compliance with the Montreal Protocol. • Differences in future emissions of CO2, CH4 and N2O between different global emissions pathways lead to large differences in ozone projections at the end of the century. • While stratospheric chlorine remains high, a large increase in stratospheric sulphate aerosol due Top panel: Variation in EESC at midlatitudes. to a major volcanic eruption or Bottom panel: Average total column ozone changes geoengineering activities would from multiple model simulations are shown as a solid result in a substantial chemical grey line. Coloured lines show ozone changes under depletion of ozone over much of four different scenarios of future greenhouse gas the globe. concentrations (WMO, 2014).

Projections of regional stratospheric ozone • Projected future ozone changes vary by region. Total column ozone changes for the Arctic in March (left) and • Ozone recovery to 1980 levels is Antarctic in October (right). The model average (red) and range expected to occur before (grey) are compared to satellite observations (blue) (WMO, midcentury in the midlatitudes 2014). and the Arctic, and somewhat later for the Antarctic ozone hole. • Significant decreases in tropical total column ozone are projected during the 21st century, except under a scenario with large increases in global Simulated tropical total column ozone for the four RCP scenarios methane emissions (RCP 8.5). (coloured lines) compared to seasonal mean total column ozone values from ground-based observations (grey) (WMO, 2014). Effects on climate from ozone depletion and recovery

Amanda Maycock, University of Leeds, UK 14 Ozone depletion has cooled the stratosphere

Change in ozone from 1979 to 1997 Change in temperature from 1979 to 1997

cooling decrease in ozone

Cruise altitude increase Surface in ozone warming

Randel et al., 2017 14 15 Ozone depletion has cooled the stratosphere

Stratospheric cooling from carbon dioxide + ozone depletion

Change in ozone from 1979 to 1997 Change in temperature from 1979 to 1997

cooling decrease in ozone

Cruise altitude increase Surface in ozone warming

Randel et al., 2017 15 16 Ozone depletion has cooled the stratosphere

Stratospheric cooling from carbon dioxide + ozone depletion

Change in ozone from 1979 to 1997 Change in temperature from 1979 to 1997

cooling decrease in ozone

Cruise altitude increase Surface in ozone warming Surface warming

Randel et al., 2017 Stratospheric cooling mainly from ozone depletion 16 Antarctic ozone depletion has caused cooling of the polar 17 stratosphere in austral spring and summer

Change in temperature over south Change in winds around south pole between 1980 and 2001 pole between 1980 and 2001 30

] warming stronger

cooling weaker

Altitude [ kilometres 2 July January July January July July

Sun et al., 2014 17 Antarctic ozone depletion has caused cooling of the polar 18 stratosphere in austral spring and summer

Change in temperature over Change in winds around south south pole between 1980 and pole between 1980 and 2001 30 2001

] warming stronger

cooling weaker

Altitude [ kilometres 2 July January July January July July Polar cooling has coincided with stronger westerly winds in stratosphere in southern spring/summer. Sun et al., 2014 18 Antarctic ozone depletion impacts on Southern hemisphere climate 19

Poleward movement of southern hemisphere westerly winds is linked to regional climate changes – surface temperatures, precipitation in WMO, 2014 midlatitudes and subtropics, Southern ocean circulation 19 Future changes in Southern hemisphere summer climate 20 determined by ozone recovery plus greenhouse gases PAST NEAR FUTURE

Tropical Tropical circulation circulation winds winds

Son et al., 2010 NOTE: Increases in greenhouse gases tend to push the region of strong westerly winds towards the pole 20 The “World Avoided” by the Montreal Protocol 21

Surface temperature change 2060-70 versus 1990-2000 World with MP: increasing CO2 and other well- mixed greenhouse gases BUT decreasing ozone North pole depleting substances

Equator

South pole

North pole

Equator

South pole World without MP: increasing CO2 and other well-mixed greenhouse gases AND increasing Red = warmer ozone depleting substances Garcia et al., 2012 21 The “World Avoided” by the Montreal Protocol 22

Surface temperature change 2060-70 versus 1990-2000 World with MP: increasing CO2 and other well- mixed greenhouse gases BUT decreasing ozone North pole depleting substances

Equator The actions of the Montreal Protocol have prevented

South pole significant further surface warming

North pole of the planet that would have occurred should emissions of CFCs have continued unabated. Equator

South pole World without MP: increasing CO2 and other well-mixed greenhouse gases AND increasing Red = warmer ozone depleting substances Garcia et al., 2012 22 (RIVM) The Netherlands

HFCs and climate protection by the Kigali amendment

Guus Velders

David Fahey, John Daniel (NOAA) Stephen Andersen (IGSD), Mack McFarland MOP29 side event: UNEP, Environment Canada, Nov. 23, 2017 Large projected HFCs emissions

● HFC emissions could offset climate benefits already achieved

● Historical emissions mainly from USA and EU

● Future emissions mainly from developing countries – China (31%) – India and other Asian countries (23%) – USA (10%), Middle East - N. Africa (11%)

• HFC emissions: 9-29% of increase of global CO2 emissions from 2015 to 2050

Velders et al. (PNAS, 2009) Velders et al. (Atmos. Env., 2015)

24 Guus Velders Kigali amendment reduces emissions

CO2-eq emissions by 2050 reduced significantly

● Developed countries: from 1  0.2 GtCO2-eq/yr

● Developing countries: from 3-4  1 GtCO2-eq/yr

25 Guus Velders Kigali amendment within reach

HFC regulations in already in place ● EU (revised F-gas regulation) ● USA (SNAP) ● Japan ● etc.

HFC regulation will drive global technological changes 

Kigali amendment within reach for most countries

26 Guus Velders Surface temperature from HFCs limited

Business as usual: up to 0.5 oC in 2100

Kigali amendment: reduced to about 0.06 oC

<1.5-2

Also important:℃ Indirect climate impacts though energy used/saved

27 Guus Velders

Ozone Monitoring – More Important than Ever!

Anne M. Thompson, PhD Senior Scientist, Atmospheric Chemistry NASA/Goddard Space Flight Center, USA

Montréal Protocol @ 30 ICAO, Montréal, 23 November 2017 Ozone: Versatile Atmospheric Actor

• Ozone’s Three Roles 1. Stratosphere: “UV Shield” 2. Tropopause: “Climate Broker” 3. Troposphere: “Double Bad Guy,” Greenhouse Gas & Major Pollutant

• Monitoring vital from pole-to-pole, <- Tropopause increasing in importance from stratosphere to ground-level

• Most sensitive regions of impact: Poles and Tropics Credit: M. Hegglin et al., UNEP/WMO, 2015 1. Stratospheric Ozone Monitoring: UV Shield

• Good News: Continuous Satellite Record • Bad News: • Stratospheric Cl measurements end when Aura/MLS & ACE/FTS end.

• Long term O3 monitoring networks threatened  Data loss 1/3 in 10 yr

2020 RISKS: DATA GAPS 1990 2000 2010 Global O3-sonde Data • Miss Reactive Cl Monitoring, Major Events, e.g. 2011 Arctic ozone “hole” • Undersampling: e.g.,Tropics – where ODS enter stratosphere & many pollutants increasing 1990 1995 2000 2005 2015 Credit: woudc.org 2. Tropopause Ozone Layer: Climate Broker

• Tropopause Layer: Conduit for ODS, other gases (H2O, N2O, CH4) to enter stratosphere

• O3 T Dynamic interactions drive future climate • BAD NEWS: Data coverage is insufficient to answer: O3 increasing or decreasing? • Require increased coverage & sampling by ground networks, ie balloons with O , 3 TL OR UT/LS H2O, and GHG instruments

Risk? Loss of key Ozone Recovery & Climate data. Trends based on remote sensing & balloon data. Credit: N. Harris et al., 2015 3. Troposphere: Profile O3 Monitoring Critical

• Good News: (1) Excellent ODS, CH4, N2O monitoring; (2) “Smog” O3 improving in many regions of world. • Bad News:

• Satellite tropospheric O3 data premature for trends. Is total tropospheric O going up or Data record ended in ... 3 1975 - 1990 2000 - 2010 1990 - 2000 2010 - 2013 down? What are climate consequences? Ground-based O3

• Model tropospheric O3 also error-prone. NO Credits: SUBSTITUTE FOR MORE: (1) O3 woudc.org, soundings; (2) routine aircraft profiles  WMO

SUMMARY: (1) O3 Monitoring needs are acute because climate is changing. As troposphere warms, “feedbacks” on smog O3, CH4, Ozone Recovery are unknown! (2) The closer to earth, the more critical is monitoring of profile O3 and related gases (3) Best News! Satellite O3 monitoring well in place. Must also Protect & Grow networks 3. Troposphere (II): Greenhouse Gases & Pollution

• Good News: Excellent tracking of ODS, N2O, CH4 • Bad News: • Most CFCs declining but other Reactive Chlorine gases are increasing! • Greenhouse gases still increasing rapidly • Reasons unclear in many cases – Keep monitoring! Add process studies!

Methane CFC-12 CH4

CFC-11

HCFC-22 HFC-134a

1975 1995 2015 Credit: NOAA (J. Elkins) • Ozone “recovery” scenarios based on unknown future Risk climate. Temperature changes may perturb tropospheric O3 in completely unanticipated ways!