The polar bear is a large bear native to the Arctic and nearby areas. It is closely related to the brown bear, and the two species can interbreed. The polar bear is the largest extant species of bear and land carnivore, with adult males weighing 300–800 kg (660–1,760 lb). The species is sexually dimorphic, as adult females are much smaller. The polar bear is white- or yellowish-furred with black skin and a thick layer of fat. It is more slender than the brown bear, with a narrower skull, longer neck and lower shoulder hump. Its teeth are sharper and more adapted to cutting meat. The paws are large and allow the bear to walk on ice and paddle in the water.
Graves' disease, also known as toxic diffuse goiter or Basedow’s disease, is an autoimmune disease that affects the thyroid. It frequently results in and is the most common cause of hyperthyroidism. It also often results in an enlarged thyroid. Signs and symptoms of hyperthyroidism may include irritability, muscle weakness, sleeping problems, a fast heartbeat, poor tolerance of heat, diarrhea and unintentional weight loss. Other symptoms may include thickening of the skin on the shins, known as pretibial myxedema, and eye bulging, a condition caused by Graves' ophthalmopathy. About 25 to 30% of people with the condition develop eye problems.
Triiodothyronine, also known as T3, is a thyroid hormone. It affects almost every physiological process in the body, including growth and development, metabolism, body temperature, and heart rate.
The endocrine system is a network of glands and organs located throughout the body. It is similar to the nervous system in that it plays a vital role in controlling and regulating many of the body's functions. Endocrine glands are ductless glands of the endocrine system that secrete their products, hormones, directly into the blood. The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testicles, thyroid gland, parathyroid gland, hypothalamus and adrenal glands. The hypothalamus and pituitary glands are neuroendocrine organs.
Susan Solomon is an American atmospheric chemist, working for most of her career at the National Oceanic and Atmospheric Administration (NOAA). In 2011, Solomon joined the faculty at the Massachusetts Institute of Technology, where she serves as the Ellen Swallow Richards Professor of Atmospheric Chemistry & Climate Science. Solomon, with her colleagues, was the first to propose the chlorofluorocarbon free radical reaction mechanism that is the cause of the Antarctic ozone hole. Her most recent book, Solvable: how we healed the earth, and how we can do it again (2024) focuses on solutions to current problems, as do books by data scientist Hannah Ritchie, marine biologist, Ayana Elizabeth Johnson and climate scientist Katharine Hayhoe.
John Scott Armstrong was an author, forecasting and marketing expert, and an Emeritus Professor of Marketing at the Wharton School of the University of Pennsylvania. Armstrong's research and writing in forecasting promote the ideas that in order to maximize accuracy, forecasting methods should rely on evidence-based methods.
Inez Fung is a professor of atmospheric science at the University of California, Berkeley, jointly appointed in the department of earth and planetary science and the department of environmental science, policy and management. She is also the co-director of the Berkeley Institute of the Environment.
Mitchell Taylor is a Canadian biologist specializing in polar bears who claims that Canada's polar bear population is higher now than it was 30 years ago and that polar bears are not currently threatened by climate change. He is currently a contract adjunct professor at Lakehead University, and he is affiliated with the Heartland Institute.
Judith A. Curry is an American climatologist and former chair of the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology. Her research interests include hurricanes, remote sensing, atmospheric modeling, polar climates, air-sea interactions, climate models, and the use of unmanned aerial vehicles for atmospheric research. She was a member of the National Research Council's Climate Research Committee, published over a hundred scientific papers, and co-edited several major works. Curry retired from academia in 2017 at age 63, coinciding with her public climate change skepticism.
Steven C. Amstrup is an American zoologist who studies bears, especially polar bears. He is the 2012 recipient of the Indianapolis Prize.
Polar Bears International (PBI) is a non-profit polar bear conservation organization. Their research, education, and action programs address the issues that are endangering polar bears. The organization also studies polar bears and monitors their activity data which helped lead to the animals being listed as a threatened species. While Churchill, Canada, serves as an important hub for PBI scientists and educators, the organization's work on behalf of polar bears spans the Arctic including Svalbard, Russia, and Alaska.
Timothy Francis Ball was a British-born Canadian public speaker and writer who was a professor in the Department of Geography at the University of Winnipeg from 1971 until his retirement in 1996. Subsequently Ball became active in promoting rejection of the scientific consensus on global warming, giving public talks and writing opinion pieces and letters to the editor for Canadian newspapers.
Pulsatile secretion is a biochemical phenomenon observed in a wide variety of cell and tissue types, in which chemical products are secreted in a regular temporal pattern. The most common cellular products observed to be released in this manner are intercellular signaling molecules such as hormones or neurotransmitters. Examples of hormones that are secreted pulsatilely include insulin, thyrotropin, TRH, gonadotropin-releasing hormone (GnRH) and growth hormone (GH). In the nervous system, pulsatility is observed in oscillatory activity from central pattern generators. In the heart, pacemakers are able to work and secrete in a pulsatile manner. A pulsatile secretion pattern is critical to the function of many hormones in order to maintain the delicate homeostatic balance necessary for essential life processes, such as development and reproduction. Variations of the concentration in a certain frequency can be critical to hormone function, as evidenced by the case of GnRH agonists, which cause functional inhibition of the receptor for GnRH due to profound downregulation in response to constant (tonic) stimulation. Pulsatility may function to sensitize target tissues to the hormone of interest and upregulate receptors, leading to improved responses. This heightened response may have served to improve the animal's fitness in its environment and promote its evolutionary retention.
Lois M. Jones was an American geochemist who led the first all-woman science team to Antarctica in 1969. They were also the first women to reach the South Pole. Jones was well regarded for her contribution to geological research in the McMurdo Dry Valleys, one of the few ice-free areas of Antarctica, and published many papers and abstracts.
Barbara Demeneix is a biologist and endocrinologist. She is currently team leader in a CNRS research unit at the National Museum of Natural History in Paris, France.
Professor Julienne Christine Stroeve is a polar climate scientist known for her research on remote sensing of ice and snow. She is Professor of Polar Observation & Modelling at the Centre for Polar Observation and Modelling, University College London, Senior Canada-150 Research Chair in Climate Forcing of Sea Ice at the University of Manitoba, and a senior research scientist at the National Snow and Ice Data Center within the Cooperative Institute for Research in Environmental Sciences (CIRES). She is also a member of the American Geophysical Union and an ISI highly cited researcher.
Katrin Juliane Meissner is a physical oceanographer and climate scientist known for climate models assessing the impact of abrupt climate change on terrestrial and marine biogeochemical cycling.
Susan M. Natali is an American ecologist. She is the Arctic program director and senior scientist at the Woodwell Climate Research Center, where her research focuses on the impact of climate change on terrestrial ecosystems, primarily on Arctic permafrost. She is also the project lead for Permafrost Pathways, a new initiative launched in 2022 with funding from TED's Audacious Project. On Monday, April 11, 2022, Dr. Natali gave a TED Talk introducing the Permafrost Pathways project at the TED2022 conference in Vancouver, BC.
Merav Ben-David is an Israeli-American ecologist, zoologist, and politician who is the chair of the Department of Zoology and Physiology at the University of Wyoming. She was the Democratic nominee in the 2020 United States Senate election in Wyoming, losing to former Congresswoman Cynthia Lummis in the general election. She ran for state representative from Wyoming's 46th District in 2022.
Polar bear population sizes and trends are difficult to estimate accurately because they occupy remote home ranges and exist at low population densities. Polar bear fieldwork can also be hazardous to researchers. As of 2015, the International Union for Conservation of Nature (IUCN) reports that the global population of polar bears is 22,000 to 31,000, and the current population trend is unknown. Nevertheless, polar bears are listed as "Vulnerable" under criterion A3c, which indicates an expected population decrease of ≥30% over the next three generations due to "decline in area of occupancy, extent of occurrence and/or quality of habitat". Risks to the polar bear include climate change, pollution in the form of toxic contaminants, conflicts with shipping, oil and gas exploration and development, and human-bear interactions including harvesting for food and possible recreational polar-bear watching.
