Editing IPCC:AR6/Glossary (section)

== H ==

<div class="glossary-entry">
<div id="Habitability"></div>
=== <span class="glossary-term">Habitability</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGII</div>

<div class="glossary-longer-term">'''Full term:''' Habitability (human)</div>

<div class="glossary-definition">'''Definition:''' The ability of a place to support human life by providing protection from hazards which challenge human survival, and by assuring adequate space, food and freshwater.</div>
</div>

<div class="glossary-entry">
<div id="Hadley_circulation"></div>
=== <span class="glossary-term">Hadley circulation</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI</div>

<div class="glossary-definition">'''Definition:''' A direct, thermally driven overturning cell in the atmosphere consisting of poleward flow in the upper troposphere, subsiding air into the subtropical anticyclones, return flow as part of the trade winds near the surface, and with rising air near the equator in the so-called Inter-tropical Convergence Zone.</div>
</div>

<div class="glossary-entry">
<div id="Halocarbons"></div>
=== <span class="glossary-term">Halocarbons</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI; WGIII</div>

<div class="glossary-definition">'''Definition:''' A collective term for the group of partially halogenated organic species, which includes the chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), halons, methyl chloride and methyl bromide. Many of the halocarbons have large global warming potentials. The chlorine and bromine-containing halocarbons are also involved in the depletion of the ozone layer.</div>
</div>

<div class="glossary-entry">
<div id="Halocline"></div>
=== <span class="glossary-term">Halocline</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI</div>

<div class="glossary-definition">'''Definition:''' A layer in the oceanic water column in which salinity changes rapidly with depth. Generally, saltier water is denser and lies below less salty water. In some high-latitude oceans the surface waters may be colder than the deep waters, and the halocline is responsible for maintaining water column stability and isolating the surface waters from the deep waters.</div>
</div>

<div class="glossary-entry">
<div id="Halosteric"></div>
=== <span class="glossary-term">Halosteric</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI</div>

<div class="glossary-definition">'''Definition:''' Density changes induced by temperature changes only are called thermosteric, while density changes induced by salinity changes are called halosteric.</div>
</div>

<div class="glossary-entry">
<div id="Halosteric_sea_level_change"></div>
=== <span class="glossary-term">Halosteric sea level change</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI</div>

<div class="glossary-definition">'''Definition:''' Halosteric sea level change occurs as a result of salinity variations: higher salinity leads to higher density and decreases the volume per unit of mass. Although both processes can be relevant on regional to local scales, only thermosteric changes impact the global mean sea level (GMSL) change, whereas the global mean halosteric change is negligible (Gregory et al., 2019).</div>
</div>

<div class="glossary-entry">
<div id="Hazard"></div>
=== <span class="glossary-term">Hazard</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI; WGII</div>

<div class="glossary-definition">'''Definition:''' The potential occurrence of a natural or human-induced physical event or trend that may cause loss of life, injury, or other health impacts, as well as damage and loss to property, infrastructure, livelihoods, service provision, ecosystems and environmental resources.</div>
</div>

<div class="glossary-entry">
<div id="Health"></div>
=== <span class="glossary-term">Health</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGII</div>

<div class="glossary-definition">'''Definition:''' Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity (WHO).</div>
</div>

<div class="glossary-entry">
<div id="Heat_index"></div>
=== <span class="glossary-term">Heat index</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI; WGII</div>

<div class="glossary-definition">'''Definition:''' A measure of how hot the air feels to the human body. The index is mainly based on surface air temperature and relative humidity and thus reflects the combined effect of high temperature and humidity on human physiology and provides a relative indication of potential health risks.</div>
</div>

<div class="glossary-entry">
<div id="Heat_stress"></div>
=== <span class="glossary-term">Heat stress</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI; WGII</div>

<div class="glossary-definition">'''Definition:''' A range of conditions in, for example, terrestrial or aquatic organisms when the body absorbs excess heat during overexposure to high air or water temperatures or thermal radiation. In aquatic water-breathing animals, hypoxia and acidification can exacerbate vulnerability to heat. Heat stress in mammals (including humans) and birds, both in air, is exacerbated by a detrimental combination of ambient heat, high humidity and low wind speeds, causing regulation of body temperature to fail.</div>
</div>

<div class="glossary-entry">
<div id="Heatwave"></div>
=== <span class="glossary-term">Heatwave</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI; WGII</div>

<div class="glossary-definition">'''Definition:''' A period of abnormally hot weather, often defined with reference to a relative temperature threshold, lasting from two days to months. Heatwaves and warm spells have various and, in some cases, overlapping definitions.</div>
</div>

<div class="glossary-entry">
<div id="Heavy_precipitation_event"></div>
=== <span class="glossary-term">Heavy precipitation event</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI; WGII</div>

<div class="glossary-definition">'''Definition:''' An extreme/heavy precipitation event is an event that is of very high magnitude with a very rare occurrence at a particular place. Types of extreme precipitation may vary depending on its duration, hourly, daily or multi-days (e.g., 5 days), though all of them qualitatively represent high magnitude. The intensity of such events may be defined with block maxima approach such as annual maxima or with peak over threshold approach, such as rainfall above 95th or 99th percentile at a particular space.</div>
</div>

<div class="glossary-entry">
<div id="Hedonic"></div>
=== <span class="glossary-term">Hedonic</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGIII</div>

<div class="glossary-definition">'''Definition:''' Subjective well-being concept based on the idea that attaining pleasure and avoiding pain leads to happiness (Ryan and Deci, 2001).</div>
</div>

<div class="glossary-entry">
<div id="Heinrich_event"></div>
=== <span class="glossary-term">Heinrich event</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI</div>

<div class="glossary-definition">'''Definition:''' Distinct layers of coarse-grained sediments comprised of ice-rafted debris identified across marine sediment cores in the North Atlantic. These sedimentary layers are closely associated with millennial-scale cooling events in the North Atlantic and a distinct pattern of global temperature and hydrological changes that are largely consistent with evidence for a slowdown, or even near-collapse, of the Atlantic Meridional Overturning Circulation (AMOC) during these times.</div>
</div>

<div class="glossary-entry">
<div id="Heterotrophic_respiration"></div>
=== <span class="glossary-term">Heterotrophic respiration</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI</div>

<div class="glossary-definition">'''Definition:''' The conversion of organic matter to 2) carbon dioxide (CO by organisms other than autotrophs.</div>
</div>

<div class="glossary-entry">
<div id="Hindcast_or_retrospective_forecast"></div>
=== <span class="glossary-term">Hindcast or retrospective forecast</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI</div>

<div class="glossary-definition">'''Definition:''' A forecast made for a period in the past using only information available before the beginning of the forecast. A sequence of hindcasts can be used to calibrate the forecast system and/or provide a measure of the average skill that the forecast system has exhibited in the past as a guide to the skill that might be expected in the future.</div>
</div>

<div class="glossary-entry">
<div id="Holocene"></div>
=== <span class="glossary-term">Holocene</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI</div>

<div class="glossary-definition">'''Definition:''' The current interglacial geological epoch, the second of two epochs within the Quaternary Period, the preceding being the Pleistocene. The International Commission on Stratigraphy (ICS) defines the start of the Holocene Epoch at 11,700 years before 2000 (Walker et al., 2019). It encompasses the mid-Holocene (MH), the 1000-year-long interval centred at 6000 years before 1950; a period of long-standing focus for climate modelling, with enhanced seasonality in the Northern Hemisphere and decreased seasonality in the Southern Hemisphere. The early part of the Holocene is marked by the late stages of deglaciation of Pleistocene land ice, sea level rise, and the occurrence of warm phases that affected different regions at different times, often referred to as the ‘Holocene Thermal Maximum’. In addition, the epoch includes the post-glacial interval, which began approximately 7000 years ago when the fundamental features of the modern climate system were essentially in place, as the influence of remnant Pleistocene ice sheets waned.</div>
</div>

<div class="glossary-entry">
<div id="Household_carbon_footprint"></div>
=== <span class="glossary-term">Household carbon footprint</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGIII</div>

<div class="glossary-definition">'''Definition:''' The carbon footprint of an individual household, inclusive of the direct and indirect carbon dioxide (CO 2) emissions associated with home energy use, transportation, food provision, and consumption of other goods and services associated with household expenditures.</div>
</div>

<div class="glossary-entry">
<div id="Human_behaviour"></div>
=== <span class="glossary-term">Human behaviour</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGII; WGIII</div>

<div class="glossary-definition">'''Definition:''' The responses of persons or groups to a particular situation, here likely to relate to climate change. Human behaviour covers the range of actions by individuals, communities, organisations, governments and at the international level.</div>
</div>

<div class="glossary-entry">
<div id="Human_influence_on_the_climate_system"></div>
=== <span class="glossary-term">Human influence on the climate system</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI</div>

<div class="glossary-definition">'''Definition:''' Human-driven activities that lead to changes in the climate system due to perturbations of the Earth’s energy budget (also called anthropogenic forcing). Human influence results from emissions of greenhouse gases, aerosols, ozone-depleting substances (ODSs), and land-use change.</div>
</div>

<div class="glossary-entry">
<div id="Human_mobility"></div>
=== <span class="glossary-term">Human mobility</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGII</div>

<div class="glossary-definition">'''Definition:''' The permanent or semi-permanent move by a person for at least 1 year and involving crossing an administrative, but not necessarily a national, border.</div>
</div>

<div class="glossary-entry">
<div id="Human_rights"></div>
=== <span class="glossary-term">Human rights</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGII; WGIII</div>

<div class="glossary-definition">'''Definition:''' Rights that are inherent to all human beings, universal, inalienable, and indivisible, typically expressed and guaranteed by law. They include the right to life, economic, social, and cultural rights, and the right to development and self-determination (UNOHCHR, 2018).</div>
</div>

<div class="glossary-entry">
<div id="Human_security"></div>
=== <span class="glossary-term">Human security</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGII; WGIII</div>

<div class="glossary-definition">'''Definition:''' A condition that is met when the vital core of human lives is protected, and when people have the freedom and capacity to live with dignity. In the context of climate change, the vital core of human lives includes the universal and culturally specific, material and non-material elements necessary for people to act on behalf of their interests and to live with dignity.</div>
</div>

<div class="glossary-entry">
<div id="Human_system"></div>
=== <span class="glossary-term">Human system</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI; WGII; WGIII</div>

<div class="glossary-definition">'''Definition:''' Any system in which human organisations and institutions play a major role. Often, but not always, the term is synonymous with society or social system. Systems such as agricultural systems, urban systems, political systems, technological systems and economic systems are all human systems in the sense applied in this report.</div>
</div>

<div class="glossary-entry">
<div id="Hydroclimate"></div>
=== <span class="glossary-term">Hydroclimate</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI</div>

<div class="glossary-definition">'''Definition:''' Part of the climate pertaining to the hydrology of a region.</div>
</div>

<div class="glossary-entry">
<div id="Hydrofluorocarbons"></div>
=== <span class="glossary-term">Hydrofluorocarbons</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI</div>

<div class="glossary-longer-term">'''Full term:''' Hydrofluorocarbons (HFCs)</div>

<div class="glossary-definition">'''Definition:''' A type of greenhouse gas (GHG), HFCs are organic compounds that contain fluorine, carbon and hydrogen atoms and they are produced commercially as a substitute for chlorofluorocarbons (CFCs). They are mainly used in refrigeration and semiconductor manufacturing.</div>
</div>

<div class="glossary-entry">
<div id="Hydrological_cycle"></div>
=== <span class="glossary-term">Hydrological cycle</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI; WGII</div>

<div class="glossary-definition">'''Definition:''' The cycle in which water evaporates from the ocean and the land surface, is carried over the Earth in atmospheric circulation as water vapour, condenses to form clouds, precipitates over the ocean and land as rain or snow, which on land can be intercepted by trees and vegetation, potentially accumulating as snow or ice, provides runoff on the land surface, infiltrates into soils, recharges groundwater, discharges into streams, and ultimately, flows into the oceans as rivers, polar glaciers and ice sheets, from which it will eventually evaporate again. The various systems involved in the hydrological cycle are usually referred to as hydrological systems.</div>
</div>

<div class="glossary-entry">
<div id="Hydrological_drought"></div>
=== <span class="glossary-term">Hydrological drought</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI; WGII</div>

<div class="glossary-definition">'''Definition:''' A period with large runoff and water deficits in rivers, lakes and reservoirs.</div>
</div>

<div class="glossary-entry">
<div id="Hydrological_sensitivity"></div>
=== <span class="glossary-term">Hydrological sensitivity</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI</div>

<div class="glossary-longer-term">'''Full term:''' Hydrological sensitivity (η)</div>

<div class="glossary-definition">'''Definition:''' The linear change in global mean precipitation per degree Celsius of global mean surface air temperature (GSAT) change once precipitation changes related to fast atmospheric and land surface adjustments to radiative forcings have occurred. Units are % per °C although it can also be calculated as W m –2 per °C.</div>
</div>

<div class="glossary-entry">
<div id="Hydropower"></div>
=== <span class="glossary-term">Hydropower</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGII; WGIII</div>

<div class="glossary-definition">'''Definition:''' Power harnessed from the flow of water.</div>
</div>

<div class="glossary-entry">
<div id="Hydrosphere"></div>
=== <span class="glossary-term">Hydrosphere</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI</div>

<div class="glossary-definition">'''Definition:''' The component of the climate system comprising liquid surface and subterranean water, such as in oceans, seas, rivers, freshwater lakes, underground water, wetlands, etc.</div>
</div>

<div class="glossary-entry">
<div id="Hyperthermal_events"></div>
=== <span class="glossary-term">Hyperthermal events</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGII</div>

<div class="glossary-definition">'''Definition:''' Geologically abrupt global warming events of the past associated with disturbances of the carbon cycle and impacts on the biosphere.</div>
</div>

<div class="glossary-entry">
<div id="Hypoxic"></div>
=== <span class="glossary-term">Hypoxic</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI; WGII</div>

<div class="glossary-definition">'''Definition:''' Conditions of low dissolved oxygen in shallow water ocean and freshwater environments. There is no universal threshold for hypoxia. A value around 60 μmol kg –1 has commonly been used for some estuarine systems, although this does not necessarily directly translate into biological impacts. Anoxic conditions occur where there is no oxygen present at all.</div>
</div>

<div class="glossary-entry">
<div id="Hypoxic_events"></div>
=== <span class="glossary-term">Hypoxic events</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGII</div>

<div class="glossary-definition">'''Definition:''' Events that lead to deficiencies of oxygen in water bodies.</div>
</div>

<div class="glossary-entry">
<div id="Hypsometry"></div>
=== <span class="glossary-term">Hypsometry</span> ===

<div class="glossary-working-groups">'''Working Groups:''' WGI</div>

<div class="glossary-definition">'''Definition:''' The distribution of land or ice surface as a function of altitude.</div>
</div>

</div>
<div class="glossary-letter-section">