The Paris Agreement: Are 1.5C a reasonable limit? Centro de Investigaciones del Mar y la Atmósfera (CIMA/UBA-CONICET) Dpto. Ciencias de la Atmósfera y los Océanos (FCEN/UBA) Instituto Franco-Argentino sobre el Clima y sus Impactos (UMI-IFAECI) Buenos Aires, Argentina

INES CAMILLONI

São Paulo, 14 July 2017

UNFCCC & the Paris Agreement

Tglobal & CO2

1.5C world

Conclusions

• A global legal instrument (international agreement) on the control and management of greenhouse gases (GHG).

• Adopted in 1992, entered into force in 1994.

• Status of participation: 197 Parties (196 States + 1 regional economic integration organization).

What is the overall goal?

“ to protect the climate system for the benefit of present and future generations of mankind. ”

What is the further objective?

“ to achieve stabilisation of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. ”

Conference of the Parties (CoP)

The COP is the supreme decision-making body of the Convention. All States that are Parties to the Convention are represented at the COP. A key task for the COP is to review the national communications and emission inventories submitted by Parties to assesses the progress made in achieving the ultimate objective of the Convention.

The COP meets every year, unless the Parties decide otherwise. The first COP meeting was held in Berlin, Germany in 1995.

The Paris Agreement: Long-Term Global Goals

• To limit warming to well below 2°C above pre-industrial levels

• To pursue efforts to limit it to 1.5°C recognizing that this would significantly reduce the risks and impacts of climate change

All Parties have to put forward their best efforts through “nationally determined contributions” (NDCs): contributions that each individual country should make in order to achieve the worldwide goal.

The Paris Agreement Nationally Determined Contributions

In 2018, Parties will take stock of the collective efforts. .

There will also be a global stocktake every 5 years to assess the collective progress towards achieving the purpose of the

Agreement.

The Paris Agreement Satus of ratification

The Paris Agreement entered into force on 4 November 2016, 30 days after the date

on which at least 55 Parties to the Convention accounting in total for at least

55 % of the total global GHGs have deposited their instruments of ratification, acceptance, approval or accession with the

Depositary.

Source: UNFCCC, 31 May 2017

28%

16% #1

#2

#3

Knutti et al. (2016)

1.5C, 2C and 4C worlds

Knutti et al. (2016)

1.5C, 2C and 4C worlds

Knutti et al. (2016)

1.5C, 2C and 4C worlds

Tglobal & CO2

Cumulative Emissions and Carbon Budget

Only the RCP2.6 scenario is in line with keeping Tglobal increase above pre-industrial levels to below 2C with a likely chance (66% probability) and no pathway is in line with a 1.5C limit.

IPCC (2013)

IPCC (2013)

Direct link between cumulative CO2 emissions and climate response

A Tglobal target can be

linked to a cumulative emissions

target

IPCC (2013)

65% of the carbon budget compatible with a 2C goal already used

IPCC (2014)

Total Carbon Budget

4-years of current emissions would be enough to blow what’s left of the carbon budget for a good chance of keeping Tglobal rise to 1.5C

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1.5C world Impacts & Avoided Risks

Reasons for concern (RFC)

The reasons for concern framework communicates scientific understanding about risks in relation to

varying levels of climate change.

The framework aggregates global risks into five categories as a function of global mean temperature change.

Reasons for concern (RFC)

RFC1: tropical glaciers, coral reefs, mangrove ecosystems, etc.

RFC2: risks from heat waves, heavy rain, drought, etc.

RFC3: impacts that affect particular groups due to uneven distribution of physical climate change hazards, exposure or vulnerability.

RFC4: impacts that can be aggregated globally according to a single metric such as lives affected, monetary damage, number of species at risk of extinction, etc.

RFC5: Large-scale abrupt and sometimes irreversible changes: i.e. disintegration of the Greenland and West Antarctic ice sheets leading to a large and rapid sea-level rise.

(IPCC,2014)

Quantitative differences

Reasons for concern (RFC)

Avoided risks

RFC 1 - Unique & threatened systems

The vast majority of tropical coral reefs will be at risk at 1.5°C

Schleussner et al. (2016)

RFC 2 - Extreme Weather Events: Extreme Precipitation

Schleussner et al. (2016)

Changes in precipitation related extremes differ substantially on the regional level

• Dry spell length or consecutive dry days (CDD): annual maximum number of consecutive days for which the precipitation is below 1mm per day.

• Heavy precipitation intensity or maximum accumulated 5-day precipitation (RX5day): absolute annual maximum of consecutive 5-day precipitation.

Dry spell length or consecutive dry days (CDD)

Heavy precipitation intensity or maximum accumulated 5-day

precipitation (RX5day)

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• Intensity of hot extremes (TXx): annual maximum value of daily maximum temperature.

• Warm spell duration indicator (WSDI): annual count of the longest consecutive period in which the daily maximum temperature for each day exceeds the 90% quantile for this day over the reference period. The minimum length is 6 consecutive days.

RFC 2 - Extreme Weather Events: Extreme Temperature

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Intensity of hot extremes (TXx) Warm spell duration

indicator (WSDI)

Smaller impacts at 1.5C

RFC 3 - Distribution of impacts: Water availability

Mediterranean ’hot-spot’ of change

Schleussner et al. (2016)

Differences in climate impacts

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1.5C Target Overshooting & Negative Emissions

Stabilization at low levels of CO2 will probably require ‘overshooting’ the concentration target.

Overshooting: CO2 Concentrations

The climate change impacts of the higher levels of GHGs concentrations reached in an overshoot profile are dependent on: • length of time the

concentrations stay above the desired target

• how far carbon dioxide overshoots

Overshooting

Rogelj and Knutti (2016)

Overshooting: Tglobal

It will be very hard – if not imposible – to keep warming below 1.5C during the entire 21st century

Negative emissions

Rogelj and Knutti (2016)

Negative Emissions

Deliberate removal of CO2 from the atmosphere by human intervention

Fuss et al (2014)

Carbon dioxide emission pathways until 2100

Examples of Negative Emissions

• Afforestation (planting trees were there were previously none) and reforestation (restoring areas where the trees have been cut down or degraded)

Examples of Negative Emissions

• Production of sustainable bioenergy with carbon

capture and storage (BECCS): Farming bioenergy crops, which extract CO2 from the atmosphere as they grow and then burning them for energy and sequestering the resulting emissions underground.

Reforestation/afforestation leads to a warming in boreal regions

Betts et al (2007)

Effects of carbon sequestration vs. surface albedo change

• The physical constraints, including sustainability of large-scale deployment relative to other land and biomass needs, such as food security and biodiversity conservation, and the presence of safe, long term storage capacity for carbon;

• The costs and financing of an untested technology

• Socio-institutional barriers, such as public acceptance of new technologies and the related deployment policies

Major uncertainties associated to BECCS

Solar Radiation Management

SRM or Solar Geoengineering: Deliberate reduction in the amount of solar radiation retained by the Earth

abrupt 4xCO2: abrupt quadrupling of CO2 from preindustrial (pi) concentrations

Geoengineering Model Intercomparison Project (GeoMIP) 12 models

G1: globally instantaneous uniform reduction in insolation to balance abrupt 4xCO2 – model dependent (3.8 – 5%)

Kravitz et al (2013)

Kravitz et al (2013)

Tropics cooler (-0.3 K) Poles warmer (+0.8 K)

Tropics cooler (-0.3 K) Poles warmer (+0.8 K)

Kravitz et al (2013)

Global rainfall reduction (4.5%) Tropical rainfall reduction

Kravitz et al (2013)

Conclusions Challenges for scientists

• Quantify local impacts of 2°C warming above the pre-industrial level

• Quantify differences of these impacts with a

1.5C warming above the pre-industrial level

• Identify which of these impacts will require adaptation and at what cost

We need to:

Conclusions Challenges for society

• Agree what risks are acceptable and which are to be avoided? (local & sector-specific)

• Demand decision-makers to aggregate local risks

to a global actionable target (1.5C - 2C)

We need to:

If the risk is high in some places and low in others, can we simply take a global average, accepting that many of

us will live dangerously?

Ethical dimensions of the discussion