Understanding Climate Hazards

Hazards and exposure

Natural or human-caused physical events can impact lives, livelihoods, ecosystems, and society. Climate change is altering the frequency and severity of these events, and some places or groups of people may experience impacts differently from others.

Climate science uncertainty and scenarios

Projecting future climate trends is challenging and inherently involves some uncertainty. This uncertainty can stem from data collection and the methods, analyses and models used to interpret data and make projections. Additionally, human choices about greenhouse gas (GHG) emission reduction levels and timelines will affect future climate conditions. Different scenarios are therefore used to represent possible futures, and projections based on these scenarios often have a range (derived from various computer models) provided to help quantify the levels of associated uncertainty. Importantly, uncertainty should not prevent us from preparing for future impacts.

The Intergovernmental Panel on Climate Change (IPCC) uses scenarios, which are representations of potential futures. IPCC scenarios combine Shared Socioeconomic Pathways (SSPs) and Representative Concentration Pathways (RCPs). SSPs describe different global social and economic development patterns and trends and RCPs detail different atmospheric GHG concentration levels (driven by different emissions levels), land use patterns, and other climate drivers. The IPCC 2021 report (section 1.6) includes more details about SSPs and RCPs.

Modeling results that we present later on this site use the SSP5-8.5 scenario. This scenario represents a future with continued rapid economic growth, which limits GHG emissions reductions yet facilitates adaptation, resulting in a 3.2°C (5.8°F) increase in median global sea surface temperature by 2100 relative to pre-industrial (1850-1900) (IPCC WG1 Interactive Atlas).

Climate Hazards

A range of climate hazards affect fisheries, and we outline some of these hazards below.

Ocean warming

The waters on the Northeast Shelf are warming rapidly–nearly three times faster than the world’s oceans since 1982. Along with this warming trend, marine heatwaves have become more frequent and intense. For the Northeast Shelf, by 2050 under SSP5-8.5, sea surface temperatures are projected to increase 1.0 - 3.5℃ (1.8 - 6.3℉) above those experienced during 1976-2005. Under the same scenario, temperatures are projected to warm 3.0 - 5.5℃ (5.4 - 9.9℉) by the end of the century.

Warming projections for this area under different climate scenarios are available via NOAA’s Climate Change Web Portal. You can find seasonal and annual warming updates for the Gulf of Maine here.

Sea level rise

Northeast US sea level has risen about 10 inches over the past 100 years (1920 – 2020), with about half of this rise occurring in the past 40 years due to thermal expansion from warming water and growing meltwater contributions from glaciers and ice sheets. If sea level rise continues along its current trajectory, 2050 sea level will be 1.3 ft (0.39 m) higher than the sea level in 2000, with a possible range of 0.9 – 2.3 ft (0.27 – 0.69 m). By 2100, sea level could rise from 1.5 – 8.1 ft (0.45 – 2.47 m). This large range is due to uncertainty in human greenhouse gas emissions and the response of ice sheets to warming. These scenarios are from the 2022 U.S. Interagency Task Force sea level technical report, which are consistent with IPCC projections.

• Interagency Sea Level Rise Scenario Tool.
• NOAA Sea Level Rise Viewer.

Ocean acidification

Ocean waters in the Northeast US, particularly in the Gulf of Maine, are also sensitive to acidification, which occurs as they absorb atmospheric carbon dioxide. Changes in carbon dioxide uptake alter the seawater chemistry, ultimately resulting in lower pH levels. The acidification effect is compounded in coastal waters, where freshwater inputs and nutrient loading further exacerbate the effects of acidification.

Ocean acidification is a concern for shell-forming organisms, such as clams, scallops and oysters, which absorb calcium and carbonate from seawater to build their shells. Aragonite is a specific form of calcium carbonate that is needed in this process. Much of the Northeast US is experiencing suboptimal aragonite saturation levels – meaning they are below 1.5 Ωar for at least a portion of the year. Future projections indicate continued declines in aragonite saturation and suboptimal saturation levels for a longer portion of the year. These effects will be most severe in nearshore coastal waters, but they are projected to expand to offshore waters, including most of the Gulf of Maine surface waters, by mid- to late-century.

Impacts on fisheries

Ocean warming, rising sea levels, and ocean acidification will have a variety of impacts on fisheries.

• Warming can influence the geographic distribution and population abundance of target species. Acute heat events may threaten the survival of animals that live in shallow waters; these same areas are threatened by deoxygenation, as warm waters cannot hold as much oxygen as cooler waters.
• Warmer oceans enable storms to intensify and last longer, which curtails fishing opportunities, threatens safety at sea, and can damage vessels and shoreside infrastructure.
• Sea level rise and higher storm surges pose risks to land-based infrastructure that supports marine fisheries, such as docks, shoreside businesses, and roads.
• Acidification threatens shell-forming organisms, whose shells may dissolve in more acidic waters. This may result in changes in availability of these species for harvesting.

Useful resources and tools

• GMRI Climate Fisheries Dashboard
• "NOAA Fisheries" Climate Information page
• Maine Department of Marine Resources Boothbay Harbor Environmental Monitoring Program
• US 2023 Fifth National Climate Assessment
• Northeast Coastal Acidification Network
• A Fishery in a Sea of Change lobster storymap

Go back to Climate Adaptation Planning for Fishing Communities homepage.