Climate change and its consequences have intensified in the period 2015-19

With only three months to go until the end of the year and take stock of the official report, the World Meteorological Organization (WMO) says that the period 2015-2019 “will probably be the warmest five-year period ever recorded” (in this case, since humans analyzed this type of data, about 130 years ago).

In addition, and perhaps more importantly, during the last five years the signs that show the existence of climate change and its most negative consequences have intensified, from the rise in sea level and the melting of ice to the increase in extreme weather events. On the other hand, the concentration of greenhouse gases in the atmosphere has also increased to unprecedented levels, “confirming a warming trend in the future.”

These three important data on the climate reality of the last five years and future forecasts are part of the WMO statement on the state of the global climate published coinciding with the start of the Climate Action Summit to be held this September 23 at the UN headquarters in New York.

WMO statement details that the global average temperature has increased by 1.1 °C since the pre-industrial era and by 0.2 °C over the period 2011-2015, and is published as part of the high-level synthesis report entitled United in Science, which has been prepared with contributions from major scientific institutions under the auspices of the Consultative Group on Climate Science of the 2019 United Nations Climate Summit United.

The report provides a joint assessment of the state of the Earth system under the growing influence of climate change, the response that humans have been able to provide to date, and the expected changes in the global climate in the future. It also highlights the potential of ambitious climate action to limit potentially irreversible effects and the imperative need to adopt them.

A related WMO greenhouse gas concentration report indicates that a continuous increase in carbon dioxide (CO) levels has been observed during the period 2015-2019.₂) and other important greenhouse gases in the atmosphere, which have reached record levels: the rate of increase in CO₂ was almost 20% higher than in the previous five years. This gas remains in the atmosphere for centuries and even longer in the oceans. According to preliminary data for 2019 and from a subset of greenhouse gas observation sites, the global _CO2 concentration should reach, or even exceed, 410 parts per million (ppm) by the end of 2019.

“The causes and effects of climate change are multiplying rather than shrinking,” said WMO Secretary-General Petteri Taalas, who is also co-chair of the United Nations Climate Summit’s Consultative Group on Climate Science.

“Sea level rise has accelerated and there are fears of an abrupt reduction in ice cover in Antarctica and Greenland, which in turn will exacerbate sea level rise in the future. As has happened this year in the Bahamas and Mozambique, where there have been tragic consequences, rising sea levels and intense tropical storms produce human and economic catastrophes.”

“We are facing great challenges. It is not only about mitigating the effects of climate change, but it is increasingly necessary to adapt to this phenomenon. According to a report recently published by the Global Commission on Adaptation, the Secretary-General noted, the most effective form of adaptation is to invest in early warning services and pay special attention to predictions that take into account impacts.”

He stressed that “it is extremely important that we reduce greenhouse gas emissions, especially those from energy production, industry and transport. This is critical to mitigating the effects of climate change and achieving the goals defined in the Paris Agreement.”

“To curb a global temperature rise of more than 2 degrees Celsius above pre-industrial levels, we must triple the level of ambition. And to limit the increase below 1.5 degrees, it is necessary to multiply it by five,” he explained.

Sea level rise

During the period 2014-2019, the global average rate of sea level rise was 5 mm per year, compared to 4 mm per year during the decade 2007-2016. This increase is well above the average rate of 3.2 mm per year recorded previously, since 1993. The contribution of melting continental ice from glaciers and ice cover to sea level rise is increasing and currently that melting, rather than thermal expansion, is the dominant element in the sea-level budget.

Reduction of ice

During the period 2015-2018, the average minimum extent of sea ice in the Arctic for the month of September (summer) was much lower than the average recorded between 1981 and 2010, and the same can be said of the average extent in winter. The four lowest winter values for which data are available occurred during that period. The multi-year ice has practically disappeared.

Antarctica

Since 2016, the minimum values of the extent of the sea ice that have been observed for February (summer) and September (winter) are much lower than the average corresponding to the period 1981-2010. These values contrast with those of the previous period of 2011-2015 and those of the longer period of 1979-2018. In Antarctica, the extent of sea ice during the summer reached its first and second lowest values in 2017 and 2018 respectively, and in 2017 the second smallest extent during the winter was also recorded.

The annual melting of Antarctica’s ice cover has increased at least sixfold, from 40 Gt per year in the period 1979-1990 to 252 Gt per year in the period 2009-2017.

The rate of melting of Greenland’s ice cover has also accelerated considerably since the beginning of the millennium.

According to the World Glacier Watch Service, the observation of the reference glaciers indicates that there has been an average change in specific mass of −908 mm of water equivalent per year, higher than that recorded for each of the five-year periods since 1950.

Ocean warming and acidification

The oceans store more than 90% of the excess heat caused by climate change. In 2018, based on measurements made up to 700 meters, the highest values of heat content of the oceans were recorded, and the years 2017 and 2015 ranked second and third respectively.

In addition, the oceans absorb approximately 30% of annual anthropogenic _CO2 emissions, thus preventing further warming. However, this represents a high ecological cost for the oceans since the _CO2 they absorb reacts with seawater thus modifying the acidity of the oceans. The level of ocean acidity has increased by 26% since the beginning of the Industrial Revolution.

Extreme weather events

More than 90% of natural disasters are weather-related. The main disasters are storms and floods, which cause the greatest economic losses. Heat waves and droughts claim human lives, stoke wildfires and lead to crop failures. Heat waves, which were the deadliest weather hazard during the 2015-2019 period, affected all continents and contributed to many new temperature records. According to one report, virtually every study that has been conducted since 2015 on significant heat waves refers to the imprint of climate change.

The largest economic losses are related to tropical cyclones. In the Atlantic, the 2017 hurricane season was one of the most devastating ever known, and the losses associated with Hurricane Harvey alone amounted to more than US$125 billion. In the Indian Ocean, in March and April 2019, Mozambique was hit by two consecutive unprecedented tropical cyclones that caused great devastation.

Forest fires

Weather and climate phenomena have a major impact on forest fires. Drought greatly increases the risk of wildfires in most forest regions, and particularly influences long-lasting fires. The forest fires causing the three largest economic losses on record have occurred over the past four years.

In many cases, fires release large amounts of _CO2 into the atmosphere. By mid-2019, unprecedented wildfires broke out in the Arctic. In the month of June alone, those fires emitted 50 megatons (Mt) of _CO2 into the atmosphere. This value exceeds the amount of _CO2 released by all the fires that occurred in the Arctic region during the same month from 2010 to 2018. In addition, large forest fires were reported in Canada and Sweden in 2018. Extensive fires were also reported in tropical rainforests in South Asia and the Amazon, where non-renewable resources are housed, affecting the global carbon budget.

Climate change and extreme events

According to the Bulletin of the Meteorological Society of the United States, during the period 2015-2017, in 62 of the 77 phenomena that were studied, a significant anthropogenic influence on the genesis of these phenomena was appreciated, and the same revealed practically all the studies carried out on important heat waves. In fact, more and more studies point to human influence in relation to the risk of extreme rainfall.

Fuetne: The Vanguard