Editing IPCC:AR6/WGI/Chapter-12 (section)

=== FAQ 12.1 | What Is a Climatic Impact-driver (CID)? ===

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A climatic impact-driver is a physical climate condition that directly affects society or ecosystems. Climatic impact-drivers may represent a long-term average condition (such as the average winter temperatures that affect indoor heating requirements), a common event (such as a frost that kills off warm-season plants), or an extreme event (such as a coastal flood that destroys homes). A single climatic impact-driver may lead to detrimental effects for one part of society while benefiting another, while others are not affected at all. A climatic impact-driver (or its change caused by climate change) is therefore not universally hazardous or beneficial, but we refer to it as a ‘hazard’ when experts determine it is detrimental to a specific system.

Climate change can alter many aspects of the climate system, but efforts to identify impacts and risks usually focus on a smaller set of changes known to affect, or potentially affect, things that society cares about. These climatic impact-drivers (CIDs) are formally defined in this Report as ‘physical climate system conditions (e.g., means, events, extremes) that affect an element of society or ecosystems. Depending on system tolerance, CIDs and their changes can be detrimental, beneficial, neutral, or a mixture of each across interacting system elements and regions’. Because people, infrastructure and ecosystems interact directly with their immediate environment, climate experts assess CIDs locally and regionally. CIDs may relate to temperature, the water cycle, wind and storms, snow and ice, oceanic and coastal processes or the chemistry and energy balance of the climate system. Future impacts and risk may also be directly affected by factors unrelated to the climate (such as socio-economic development, population growth, or a viral outbreak) that may also alter the vulnerability or exposure of systems.

CIDs capture important characteristics of the average climate and both common and extreme events that shape society and nature (see FAQ 12.2). Some CIDs focus on aspects of the average climate (such as the seasonal progression of temperature and precipitation, average winds or the chemistry of the ocean) that determine, for example, species distribution, farming systems, the location of tourist resorts, the availability of water resources and the expected heating and cooling needs for buildings in an average year. CIDs also include common episodic events that are particularly important to systems, such as thaw events that can trigger the development of plants in spring, cold spells that are important for fruit crop chill requirements, or frost events that eliminate summer vegetation as winter sets in. Finally, CIDs include many extreme events connected to impacts such as hailstorms that damage vehicles, coastal floods that destroy shoreline property, tornadoes that damage infrastructure, droughts that increase competition for water resources, and heatwaves that can strain the health of outdoor labourers.

Many aspects of our daily lives, businesses and natural systems depend on weather and climate, and there is great interest in anticipating the impacts of climate change on the things we care about. To meet these needs, scientists engage with companies and authorities to provide climate services – meaningful and possibly actionable climate information designed to assist decision-making. Climate science and services can focus on CIDs that substantially disrupt systems to support broader risk management approaches. A single CID change can have dramatically different implications for different sectors or even elements of the same sector, so engagement between climate scientists and stakeholders is important to contextualize the climate changes that will come. Climate services responding to planning and optimization of an activity can focus on more gradual changes in operating climate conditions.

FAQ 12.1, Figure 1 tracks example outcomes of seasonal snow cover changes that connect climate science to the need for mitigation, adaptation and regional risk management. The length of the season with snow on the ground is just one of many regional climate conditions that may change in the future, and it becomes a CID because there are many elements of society and ecosystems that rely on an expected seasonality of snow cover. Climate scientists and climate service providers examining human-driven climate change may identify different regions where the length of the season with snow cover could increase, decrease, or stay relatively unaffected. In each region, change in seasonal snow cover may affect different systems in beneficial or detrimental ways (in the latter case, changing seasonal snow cover would be a ‘hazard’), although systems such as coastal aquaculture remain relatively unaffected. The changing profile of benefits and hazards connected to these changes in the seasonal snow cover CID affects the profile of impacts, risks and benefits that stakeholders in the region will grapple with in response to climate change.

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'''FAQ 12.1, Figure 1 |''' '''A single climatic impact-driver can affect ecosystems and society in different ways.''' A variety of impacts from the same climatic impact-driver change, illustrated with the example of regional seasonal snow cover.

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