Understanding the Present Climate Change


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A series of photos shows the Grinnel Glacier in the years 19 38, 19 81, 19 98 and 2009. In 19 38, the lake beneath the glacier was completely frozen. In 19 81, about one-third of the lake was thawed. In 19 98, two-thirds of the lake was thawed. In 2009, it was covered with chunks of ice, but otherwise it was completely thawed. At the same time, the glacier itself has steadily receded.
The effect of global warming can be seen in the continuing retreat of Grinnel Glacier. The mean annual temperature in the park has increased 1.33 °C since 1900. The loss of a glacier results in the loss of summer meltwaters, sharply reducing seasonal water supplies and severely affecting local ecosystems. (credit: modification of work by USGS)

OpenStax Biology 2e

A number of global events have occurred that may be attributed to climate change during our lifetimes. Glacier National Park in Montana is undergoing the retreat of many of its glaciers, a phenomenon known as glacier recession. In 1850, the area contained approximately 150 glaciers. By 2010, however, the park contained only about 24 glaciers greater than 25 acres in size. One of these glaciers is the Grinnell Glacier at Mount Gould. Between 1966 and 2005, the size of Grinnell Glacier shrank by 40 percent. Similarly, the mass of the ice sheets in Greenland and the Antarctic is decreasing: Greenland lost 150–250 km3 of ice per year between 2002 and 2006. In addition, the size and thickness of the Arctic sea ice is decreasing.

This loss of ice is leading to increases in the global sea level. On average, the sea is rising at a rate of 1.8 mm per year. However, between 1993 and 2010 the rate of sea level increase ranged between 2.9 and 3.4 mm per year. A variety of factors affect the volume of water in the ocean, especially the temperature of the water (the density of water is related to its temperature: water volume expands as it warms, thus raising sea levels), as well as the amount of water found in rivers, lakes, glaciers, polar ice caps, and sea ice. As glaciers and polar ice caps melt, there is a significant contribution of liquid water that was previously frozen.

In addition to some abiotic conditions changing in response to climate change, many organisms are also being affected by the changes in temperature. Temperature and precipitation play key roles in determining the geographic distribution and phenology of plants and animals. (Phenology is the study of the effects of climatic conditions on the timing of periodic life cycle events, such as flowering in plants or migration in birds.) Researchers have shown that 385 plant species in Great Britain are flowering 4.5 days sooner than was recorded earlier during the previous 40 years. In addition, insect-pollinated species were more likely to flower earlier than wind-pollinated species. The impact of changes in flowering date would be mitigated if the insect pollinators emerged earlier. This mismatched timing of plants and pollinators could result in injurious ecosystem effects because, for continued survival, insect-pollinated plants must flower when their pollinators are present.


Clark, M., Douglas, M., Choi, J. Biology 2e. Houston, Texas: OpenStax. Access for free at: https://openstax.org/details/books/biology-2e


Related Research Articles from PubMed

Indiscriminate, Irrelevant, and Sometimes Wrong: Causal Misconceptions about Climate Change

Prior research demonstrates widespread persistence of beliefs about climate change causes and risks that are arguably misconceptions. They include believing pollution causes climate change, believing ozone depletion causes climate change, the combination of these two “green beliefs,” referred to as environmental problems, and believing natural climate variation significantly contributes to current climate trends. Each of these causal beliefs has the potential to weaken or divert support away from effective climate change risk mitigation policies. To assess this potential, we explore the nature and prevalence of these beliefs in the United States with a national sample of interviews (N = 77) and two national surveys (N = 1,013, N = 1,820), and apply regression and mediation analyses to explore whether they explain any of the variation in individuals’ concern or support for policy to mitigate climate change. Adherence to these beliefs-which reflect a variety of misconceptions illustrated in the interviews-differs by political ideology but is common, with over a third of interviewees mentioning one or more. Controlling for general knowledge, political ideology, and other factors, misconceptions about environmental problems are still associated directly with support for climate change policies. On average adherence to the belief that environmental problems cause climate change is associated with a 25% higher probability of policy support. In contrast, believing natural climate variability is a major recent cause of climate change is associated with a 7% lower probability of supporting climate policy, even after controlling for political ideology and other knowledge about climate change.

Keywords: Climate change; mental models; risk perceptions.


No safety net in the face of climate change: The case of pastoralists in Kunene Region, Namibia

Over the past decade, pastoralists in Kunene Region, Namibia, have endured recurrent drought and flood events that have culminated in the loss of their primary form of livelihood-pastoralism. Most pastoralists are finding it difficult to sustain their livelihoods, and their communities have fallen into extreme poverty. Ecosystem-based Adaptation (EbA) approaches are increasingly acknowledged as having the potential to enhance the adaptive capacity of vulnerable communities. The first step is to develop an understanding of how affected communities live, their perceptions of and how they respond to climate change and the biophysical impacts of climate change in their communities. This study aims to collect this information in order to explore the use of EbA to help pastoralists adapt to climate change. We examined an isolated pastoral Himba community, to understand their perceptions, experiences and understanding of climate change and its related impacts on their livelihoods. A nested mixed-methods approach using structured interviews was employed to address the study objectives. Interview results revealed that pastoralists lack scientific knowledge of climate change, and they have no access to climate change information. Though pastoralists have coping and adaptation approaches at the community level (such as making gardens, fishing, etc.), these have become ineffective as climatic uncertainty and change persist. Furthermore, pastoralists no longer get benefits from the environment, such as food and fodder. Despite this, there are currently no biodiversity interventions at the community level to address the impacts of climate change. Pastoralists have indicated their adaptation needs, particularly the provision of water supply to grow food. This is an open avenue to explore EbA approaches, specifically ecological restoration, while still addressing the need of the pastoralists. There is an urgent need to develop new practical adaptation strategies, including restoration options that will strengthen their adaptive capacity.


Insects in high-elevation streams: life in extreme environments imperiled by climate change

Climate change is altering conditions in high-elevation streams worldwide, with largely unknown effects on resident communities of aquatic insects. Here, we review the challenges of climate change for high-elevation aquatic insects and how they may respond, focusing on current gaps in knowledge. Understanding current effects and predicting future impacts will depend on progress in three areas. First, we need better descriptions of the multivariate physical challenges and interactions among challenges in high-elevation streams, which include low but rising temperatures, low oxygen supply and increasing oxygen demand, high and rising exposure to ultraviolet radiation, low ionic strength, and variable but shifting flow regimes. These factors are often studied in isolation even though they covary in nature and interact in space and time. Second, we need a better mechanistic understanding of how physical conditions in streams drive the performance of individual insects. Environment-performance links are mediated by physiology and behavior, which are poorly known in high-elevation taxa. Third, we need to define the scope and importance of potential responses across levels of biological organization. Short-term responses are defined by the tolerances of individuals, their capacities to perform adequately across a range of conditions, and behaviors used to exploit local, fine-scale variation in abiotic factors. Longer-term responses to climate change, however, may include individual plasticity and evolution of populations. Whether high-elevation aquatic insects can mitigate climatic risks via these pathways is largely unknown.

Keywords: aquatic insects; evolution; flow; oxygen; physiology; plasticity; temperature; ultraviolet radiation.


Climate change and dengue fever knowledge, attitudes and practices in Bangladesh: a social media-based cross-sectional survey

Background: Bangladesh experienced its worst dengue fever (DF) outbreak in 2019. This study investigated the knowledge, attitudes and practices (KAP) among university students in Bangladesh and significant factors associated with their prevention practices related to climate change and DF.

Methods: A social media-based (Facebook) cross-sectional KAP survey was conducted and secondary data of reported DF cases in 2019 extracted. Logistic regression and spatial analysis were run to examine the data.

Results: Of 1500 respondents, 76% believed that climate change can affect DF transmission. However, participants reported good climate change knowledge (76.7%), attitudes (87.9%) and practices (39.1%). The corresponding figures for DF were knowledge (47.9%), attitudes (80.3%) and practices (25.9%). Good knowledge and attitudes were significantly associated with good climate change adaptation or mitigation practices (p<0.05). Good knowledge, attitudes and previous DF experiences were also found to be significantly associated with good DF prevention practices (p<0.001). There was no significant positive correlation between climate change and DF KAP scores and the number of DF cases.

Conclusions: Findings from this study provide baseline data that can be used to promote educational campaigns and intervention programs focusing on climate change adaptation and mitigation and effective DF prevention strategies among various communities in Bangladesh and similar dengue-endemic countries.

Keywords: adaptation; climate change; control; dengue; early warning system; prevention.


Tropical and Mediterranean biodiversity is disproportionately sensitive to land-use and climate change

Global biodiversity is undergoing rapid declines, driven in large part by changes to land use and climate. Global models help us to understand the consequences of environmental changes for biodiversity, but tend to neglect important geographical variation in the sensitivity of biodiversity to these changes. Here we test whether biodiversity responses to climate change and land-use change differ among biomes (geographical units that have marked differences in environment and species composition). We find the strongest negative responses to both pressures in tropical biomes and in the Mediterranean. A further analysis points towards similar underlying drivers for the sensitivity to each pressure: we find both greater reductions in species richness in the types of land use most disturbed by humans and more negative predicted responses to climate change in areas of lower climatic seasonality, and in areas where a greater proportion of species are near their upper temperature limit. Within the land most modified by humans, reductions in biodiversity were particularly large in regions where humans have come to dominate the land more recently. Our results will help to improve predictions of how biodiversity is likely to change with ongoing climatic and land-use changes, pointing toward particularly large declines in the tropics where much future agricultural expansion is expected to occur. This finding could help to inform the development of the post-2020 biodiversity framework, by highlighting the under-studied regions where biodiversity losses are likely to be greatest.


Antarctic intertidal macroalgae under predicted increased temperatures mediated by global climate change: Would they cope?

The Antarctic Peninsula is one of the regions to be most affected by increase in sea surface temperatures (SSTs) mediated by Global Climate Change; indeed, most negative predictions imply an up to 6 °C increment by the end of the XXI century. Temperature is one of the most important factors mediating diversity and distribution of macroalgae, although there is still no consensus as to the likely effects of higher SSTs, especially for polar seaweeds. Some available information suggests that potential strategies to withstand future increases in SSTs will be founded upon the glutathione-ascorbate cycle and the induction of chaperone-functioning heat shock proteins (HSPs); however, their eventual role, even for general stress responses, is unclear. The intertidal green, brown and red macroalgae species Monostroma hariotii, Adenocystis utricularis and Pyropia endiviifolia, respectively, from King George Island, Antarctic Peninsula, were exposed to 2 °C (control) and 8 °C (climate change scenario) for up to 5 days (d). Photosynthetic activity (αETR and ETRmax, and EkETR), photoinhibition (Fv/Fm) and photoprotection processes (αNPQ, NPQmax, and EkNPQ) provided no evidence of negative ecophysiological effects. There were moderate increases in H2O2 production and levels of lipid peroxidation with temperature, results supported by stable levels of total glutathione and ascorbate pools, with mostly higher levels of reduced ascorbate and glutathione than oxidized forms in all species. Transcripts of P. endiviifolia indicated a general upregulation of all antioxidant enzymes and HSPs genes studied under warmer temperature, although with different levels of activation with time. This pioneering investigation exploring different levels of biological organization, suggested that Antarctic intertidal macroalgae may be able to withstand future rise in SSTs, probably slightly altering their latitudinal distribution and/or range of thermal tolerance, by exhibiting robust glutathione-ascorbate production and recycling, as well as the induction of associated antioxidant enzymatic machinery and the syntheses of HSPs.

Keywords: Extremophiles; Global warming; Phaeophyceae; Rhodophyceae; Ulvophyceae.



Keywords: current climate change, climate change today, what is climate change, effects of climate change, causes of climate change, research about climate change, climate change research