The Intergovernmental Panel on Climate Change (“IPCC”) issued its Sixth Assessment Report (“AR6”) on March 19, 2023 summarizing the findings of various studies of the impacts of climate change. “This Synthesis Report (SYR) of the IPCC Sixth Assessment Report (AR6) summarizes the state of knowledge of climate change, its widespread impacts and risks, and climate change mitigation and adaptation.”
The Report notes that global surface temperatures between 2011- 2020 were on average 1.09 degrees Celsius higher than the period of 1850 -1900. With the temperature over land averaging about half a degree Celsius more than over oceans. The “likely” amount of the increase due to human activity represented by Greenhouse Gases (“GHGs”) and aerosols is 1.07 degrees Celsius.
Some of the findings,noted in the Report follow, with notations as to the level of confidence in the accuracy of the conclusions:
“Evidence of observed changes in extremes such as heatwaves, heavy precipitation, droughts, and tropical cyclones, and, in particular, their attribution to human influence, has further strengthened since AR5. Human influence has likely increased the chance of compound extreme events since the 1950s, including increases in the frequency of concurrent heatwaves and droughts (high confidence) ….
Between 2010 and 2020, human mortality from floods, droughts and storms was 15 times higher in highly vulnerable regions, compared to regions with very low vulnerability. (high confidence) …
Climate change has caused substantial damages, and increasingly irreversible losses, in terrestrial, freshwater, cryospheric, and coastal and open ocean ecosystems (high confidence). Hundreds of local losses of species have been driven by increases in the magnitude of heat extremes (high confidence) with mass mortality events recorded on land and in the ocean (very high confidence). Impacts on some ecosystems are approaching irreversibility such as the impacts of hydrological changes resulting from the retreat of glaciers, or the changes in some mountain (medium confidence) and Arctic ecosystems driven by permafrost thaw (high confidence) ….
Climate change has reduced food security and affected water security, hindering efforts to meet Sustainable Development Goals (high confidence) ….
In all regions increases in extreme heat events have resulted in human mortality and morbidity (very high confidence). The occurrence of climate-related food-borne and water-borne diseases (very high confidence) and the incidence of vector-borne diseases (high confidence) have increased. In assessed regions, some mental health challenges are associated with increasing temperatures (high confidence), trauma from extreme events (very high confidence), and loss of livelihoods and culture (high confidence) ….
Climate change has caused widespread adverse impacts and related losses and damages to nature and people that are unequally distributed across systems, regions and sectors. Economic damages from climate change have been detected in climate-exposed sectors, such as agriculture, forestry, fishery, energy, and tourism….
In urban areas, observed climate change has caused adverse impacts on human health, livelihoods and key infrastructure. Hot extremes have intensified in cities. Urban infrastructure, including transportation, water, sanitation and energy systems have been compromised by extreme and slow-onset events, with resulting economic losses, disruptions of services and negative impacts to well-being. Observed adverse impacts are concentrated amongst economically and socially marginalised urban residents. (high confidence) …”
The Report goes on to assess adaptation attempts, noting that, while adaptation is increasing and brings improvements, it is spotty and needs to be increased. “Most observed adaptation responses are fragmented, incremental, sector-specific and unequally distributed across regions. Despite progress, adaptation gaps exist across sectors and regions, and will continue to grow under current levels of implementation, with the largest adaptation gaps among lower income groups “
The Report projects continued increases in global warming in the “near term (2021-2040)”. “The assessed climate response to GHG emissions scenarios results in a best estimate of warming for 2081–2100 that spans a range from 1.4°C for a very low GHG emissions scenario … to 2.7°C for an intermediate GHG emissions scenario … and 4.4°C for a very high GHG emissions scenario…”.
In addition, it further notes that we have reached certain irreversible changes, resulting from the cumulative impacts of climate change which include, among other manifestations:
“Limiting global surface temperature does not prevent continued changes in climate system components that have multi-decadal or longer timescales of response (high confidence). Sea level rise is unavoidable for centuries to millennia due to continuing deep ocean warming and ice sheet melt, and sea levels will remain elevated for thousands of years (high confidence). However, deep, rapid and sustained GHG emissions reductions would limit further sea level rise acceleration and projected long-term sea level rise commitment….
The likelihood and impacts of abrupt and/or irreversible changes in the climate system, including changes triggered when tipping points are reached, increase with further global warming (high confidence). As warming levels increase, so do the risks of species extinction or irreversible loss of biodiversity in ecosystems including forests (medium confidence), coral reefs (very high confidence) and in Arctic regions (high confidence). …The probability and rate of ice mass loss increase with higher global surface temperatures (high confidence)…”
It is noted in the Report that options for adaptation decrease as the situation worsens and piecemeal attempts at adaptation could even worsen the long term impacts. Currently, the Report projects exceeding the 1.5 degree Celsius level that has been viewed as a tipping point, but notes concerted efforts could limit the degree of “overshoot” and ultimately bring GHG levels down and possibly eventually reverse the global increase in temperatures. But it predicts that the global impacts will be severe, long lasting and in some instances permanent, or certainly long lasting (for millennia). Most disconcerting is that the Report projects more severe impacts than previously forecast.