donald boesch blue planet forum presentation

Climate Change: Causes & Consequences

Donald F. Boesch

APRIL 25, 2017

Observed Warming Can Only Be Explained by Human Influences

“I would not agree that [carbon dioxide] is a primary contributor to the global warming that we see. We don’t know that yet, we need to continue the debate and the review and analysis.”

Scott PruittEPA Administrator Climate models run with only natural factors (primarily solar

intensity and volcanoes) and with both natural and human factors (primarily greenhouse gas concentrations)

How Much Warming Is Due to Human Activities?

Approximately all of it!

Fractional attribution to human causes

170 times natural factors

25% 50% 75% 100% 125% 150% 175%

110%

IPCC Fifth Assessment

No Surprise as Atmospheric Greenhouse Gases Have Increased

43.5% increase over pre-industrial concentrations

CO2 responsible for about 75% of GHG effect.Methane, nitrous oxide, CFCs most of the rest.

Concentration not seen in 4 million years

Need More Evidence?Lower Stratosphere Is Cooling

Lower stratosphere cooling

Lower troposphere & surface warming

Observed Warming Is Consistent with Climate Models

Update from Hausfather et al. 2017

1998 ENSO

2015-2016 ENSO

The Heat is Being Stored in the Ocean

Bay Waters Have Been Warming

Najjar et al. 2010. Estuarine, Coastal, Shelf Science 86:1

Ding & Elmore 2015. Remote Sensing of Environment 168: 335

Landsat satellite records: surface water warming 0.05 to 0.10° C per year, 1985-2012

Average annual temperature

(since 1985 about 0.14° F per year on average)

(almost 3° F since 1940s)

It mainly depends on how much greenhouse gases we emit.

How Much Will Earth Warm?

Global average surface temperature

Unrestrained growth in emissions

RCP 8.5

Rapid emissions reductions

RCP 2.6

7.2°F

3.6°F

www.ipcc.ch

Where we are headed

2.0°C Paris Agreement1.5°C More ambitious

We are here!

The Greater the Warming, the Greater the Risks

Maryland GGRA

Paris Agreement:

US intended reductions

Global

emissions

likely to

avoid 2°C

Pe

rce

nt

of

20

05

em

iss

ion

s

US

emissions

must be in

this range

40 by 30

25 by 20

Limiting Warming Requires Rapid Reduction of GHG Emissions

Sea-Level Has Been Rising since 19th Century

Norfolk tide gauge

Sea-level Rise in Chesapeake Bay Region

4.08 mm y-1

4.31 mm y-1

4.14 mm y-1

4.88 mm y-1

4.39 mm y-1

5.86 mm y-1

3.93 mm y-1

5.55 mm y-1

Sea-level rise1983-2013

Kopp et al. 2014. Earth’s Future

67-124 cm

44-85 cm

RCP 8.5

Sea-level Rise Projections for Baltimorewith polar ice melt & vertical land motion

Likely

RCP 2.6

Compared with 5 DoD scenarios adjusted for subsidence

Unrestrained growth in emissions

RCP 8.5

Rapid emissions reductions

RCP 2.6

Wild Card: Polar Ice Sheets

Mann & Kump 2008

Precipitation Patterns Also Affected

Sea surface temperature anomaly

Extreme Events Linked to Climate ChangeAugust 2016 Louisiana floods

• Climate change is real, primarily caused by humans and very dangerous.

• Sea-level rise will accelerate. The Bay will continue to warm, hold more water and receive more winter-spring runoff.

• We should begin to adapt and become resilient to these and other unavoidable climate changes.

• However, adaptation only will become a losing proposition by later this century.

• Without dramatic reduction in global greenhouse gas emissions by mid-century we will be confronted with conditions to which we cannot effectively adapt.

• In other words, we must manage the unavoidable while also avoiding the unmanageable.

What Science is Telling Us

boesch@umces.edu

www.umces.edu/don-boesch @DonBoesch