climate change

flooding and extreme rainfall

- In August 2019, the south-west Indian state of Kerala suffered major flooding, reportedly the worst since 1924, as a result of persistent heavy monsoon rains. Total economic losses were estimated at US$ 4.3 billion.

Surface Temperature

- Warming since the mid-18th century is estimated to be around 1.1 degree Celsius. -The surface temperature has been increasing by 0.1 degree Celsius every 5-6 years since the 1970s. -2015, 2016, 2017 and 2018 are the four warmest years on record. -Graph: Global mean temperature anomalies with respect to the 1850-1900 baseline, for the five global datasets (Source: UK Met Office Hadley Centre)

Projections

Climate projections help us predict the response of the climate system to actors such as the concentration of GHG emissions. Projections depend on assumptions about future socioeconomic and technological developments. For example, the uptake of renewable energies.

learned

Having reliable information is of critical importance for reducing climate risks and formulating action to reduce and adapt to a changing climate. To collect data, monitor and predict changes in the weather and climate a complex international system had been created. This system is constantly evolving to account for numerous climate variables. The data amassed is used by scientists to produce credible reports that policymakers and business leaders need to make evidence-based decisions.

learned

IPCC's climate risk framework helps us to differentiate between the different aspects of climate impacts, such as specific hazards, exposed assets and local vulnerability. Through this lens, we see the different ways in which the planet, as a whole, and different geographical regions are affected by the changes in climate.

A global surface temperature change of 1.5°C is among the most optimistic scenarios. Yet, it will still significantly affect our climate indicators.

Sea level 0.26 to 0.77 m global mean sea level rise (relative to 1986-2005) Ocean heat and acidification Coral reefs are projected to decline by a further 70-90%. Global annual catch for marine fisheries will decrease by 1.5 million tonnesTemperature anomalies 3°C hotter extreme hot days in mid-latitudes 4.5°C warmer extreme cold nights in high latitudes Source: IPCC, 2018: Summary for Policymakers. In: Global Warming of 1.5°C.

What Have You Learned?

We use climate indicators, such as temperature, sea level and ocean acidification, to describe and track the state of the climate. Greenhouse gas emissions have caused a 1.0°C rise in the global temperature over the past 150 years. The ocean has become hotter and more acid. Glaciers and sea ice are losing mass. These global changes will continue as carbon dioxide continues to accumulate.

Models

a climate model is a complex software which aims to reproduce as faithfully as possible the real climate system through mathematical simulations. Because of the numerous variables related to those complex processes, climate science prepares different models and compares them (see: IPCC Coupled Model Intercomparison Project).

aerosol

a colloidal solution dispensed as a mist

Forecasts

a weather forecast is a prediction of what the weather will be like in the short to medium term. Weather forecasts are typically accurate up to 7 days in advance. A climate forecast or climate prediction is generated on a seasonal, interannual or long-term timescale.

Small Island and Developing States or SIDS

are a distinct group of 58 countries located in the Caribbean Sea, Pacific, Atlantic and Indian Oceans and the South China Sea. SIDS have a special case status because of their small size, remoteness and narrow resource base which, in comparison with other countries, make them inherently vulnerable to climate change. Their total population of around 65 million people has contributed less than 1% of global GHG emissions.

heatwaves

- 2018 was the fourth warmest year on record - the fourth one in a row! In itself, this does not constitute an extreme heat event, which occurs when the daily maximum temperature of more than five consecutive days exceeds the average maximum temperature by 5 °C (9 °F), the normal period being 1961-1990. The period May to July 2018 was the driest and warmest periods on record for most of Scandinavia (observations dating back to 1748). A prolonged heatwave in late July and early August (see image) included numerous records north of the Arctic Circle, and record long runs of 25 consecutive days above 25 °C in Helsinki, Finland (Source: WMO, Statement on the State of the Global Climate in 2018).

Sea Level

- Global mean sea level in 2016 was the highest yearly average since measurements started in the late 19th century. The rate of sea level rise since 1993, when satellite measurements became available, is around 3 mm/year, compared to 1.2 to 1.7 mm/year prior. In 2018, the total sea level change since 1993 was 78 mm. Graph: Observed change in global mean sea level from 1880 to 2015 based on three sources. All values are relative to the average level of the period 1993-2012.

500000-100000 yrs ago

500,000 - 100,000 years ago a period of hot and cold fluctuations occurred. Samples from the Arctic ice show that over a period of several hundred thousand years, the great ice sheets that covered parts of North America and Europe have melted in a series of temperature surges, each one occurring approximately every 100,000 years. This leads us to the last 10,000 years.

carbon futures

By adding carbon data into climate models, scientists have come up with different possible emissions pathways leading us to the year 2100. Depending on the amounts of greenhouse gas emissions in the atmosphere, different global mean surface temperature changes are projected. This lesson covers: 4 emission pathways limiting the temperature increase to 1.5°C or 2°C by 2100. No-climate-policy baseline leading to a temperature increase of +3°C by 2100.

past two billion years

During the last 2 billion years the Earth's climate has alternated between a frigid "Ice House", and a steaming "Hothouse", like the world of the dinosaurs. During the 'greenhouse' period, there is a lot more liquid water on the planet, while during 'icehouse' world the climate is cold enough to support large sheets of ice, sometimes covering the entire planet.

What causes changes in climate?

Earth's climate does not change without a reason. Many factors may influence it over long periods of time. Such factors are known as "climate forcings". 3 main climate drivers: 1) solar variability, 2) volcanic activities and 3) changes in the carbon cycle.

Greenhouse Gases

In 2017, the global levels of CO2 concentration in the atmosphere passed 405 parts per million (ppm) and will not decrease for generations to come. This does not include other greenhouse gases or aerosols, which also affect the climate. The concentration of other greenhouse gases such as CH4 and N2O were also the highest on record in 2018. Together, land-use change and fossil CO2 emissions reached an estimated 41.5 ± 3.0 billion tons of CO2 in 2018. You might find this also expressed in gigatons or GtCO2. Check for yourself: Global monthly mean carbon dioxide globally averaged over marine surface sites since 1980 (Source: The Global Monitoring Division of NOAA/Earth System Research Laboratory)

ocean acidity

In the past decade, the oceans absorbed around 25% of anthropogenic carbon dioxide emissions. The absorbed carbon dioxide reacts with seawater and leads to ocean acidification. Ocean surface pH has declined from 8.2 to below 8.1 over the industrial era as a result of the increase in atmospheric CO2 concentrations. This decline corresponds to an increase in oceanic acidity of about 30 %. Ocean acidification in recent decades has been occurring 100 times faster than during past natural events over the last 55 million years.

What is the Role of Credible Data and Analysis

It is hard to trust one's senses when it comes to credibly assess climate change. Over time, a complex system that collects data and produces credible analysis has been developed

Ocean Heat

More than 90% of the energy trapped by greenhouse gases goes into the oceans. The global surface temperature has been rising slowly because our oceans have been absorbing most of the excess energy in the climate system. Warming of the upper (0-700 metres) ocean accounted for about 64 % of the total heat uptake. Recent observations also show substantial warming of the deeper ocean (between depths of 700 and 2,000m and below 3,000m). Graph: Time series of global ocean heat content at different depths. (Source: European Environment Agency/ Data: National Oceanic and Atmospheric Administration (NOAA))

Carbon emissions leading to a 2°C temperature change is the greatest tolerable change. It will still vastly affect our climate indicators.

Sea level 0.30 to 0.83 m global mean sea level rise (relative to 1986-2005)10 million more people exposed to sea-level rise risks (relative to >1.5°C)Ocean heat and acidification Coral reefs are projected to decline by 99% Global annual catch for marine fisheries will decrease by 3 million tonnes Temperature anomalies 4°C hotter extreme hot days in mid-latitudes 6°C warmer extreme cold nights in high latitudes OtherHigher risks from heavy precipitation and droughtsHigher risks from forest firesRisks from some vector-borne diseases, such as malaria and dengue fever Source: IPCC, 2018: Summary for Policymakers. In: Global Warming of 1.5°C.

How is the climate changing there?

Sea-level rise inundating low-lying areas Changing rainfall patterns Warming and acidification of coastal waters (coral bleaching) Storms and flooding (destroying tourist resorts and residential area) Land erosion Changes in the global water cycle (moving fisheries away) Saline intrusion into terrestrial systems Degrading ecosystems and habitat loss Species shifts in terrestrial systems Climate-induced diseases Increased weather intensity (casualties and damage)

There are two polar regions, the Arctic (North) and Antarctica (South).

The Arctic is a region, centred around the North Pole, which includes the ice-covered Arctic Ocean and landmasses from Scandinavia, Greenland, Canada and Alaska. It is the warmer pole and parts of it are habitable year-round. Antarctica is a continent centred around the South Pole. It holds 90% of the world's ice and 70% of the freshwater and is the world's coldest corner. The continent doesn't have native people or large terrestrial mammals but boasts an incredibly diverse marine life with microscopic plankton, whales and about 100 species of fish.

The Global Climate Observing System

The Global Climate Observing System (GCOS) was established in 1992 to ensure that the observations and information needed to address climate-related issues are obtained and made available to all potential users. The goal of GCOS is to provide comprehensive information on the total climate system, including a range of physical, chemical and biological properties and atmospheric, oceanic, hydrologic, cryospheric and terrestrial processes.

Sea Ice

The extent and volume of Arctic sea ice have declined rapidly since global data became available, especially in summer. In each year between 2007 and 2018, Arctic summer sea ice extent was lower compared to any previous year since the introduction of satellites in 1979. The largest bodies of ice, the Greenland and Antarctic ice sheets, have been losing large amounts of ice at an increasing rate since 1992. Graph: Cumulative ice mass loss from Greenland and Antarctica. (Source: European Environment Agency/ Data: University of Leeds)

A Decade of Climate Extremes

The first decade of the 21st century was the warmest decade recorded since modern measurements began around 1850. It saw above-average precipitation, along with a number of extreme weather events. A decadal perspective makes it possible to assess trends and anticipate the future. It can also inform efforts to develop operational climate services that provide information and forecasts for decision-making in agriculture, health, disaster risk, water resources and other sectors. Some of the major heatwaves of the 2001-2010 decade of extremes are highlighted on the map. (Source: WMO, 2013, The Global Climate 2001 - 2010)

Climate System

The global geosystem that includes all the components of the Earth system and all the interactions among these components needed to determine climate on a global scale and how it changes over time. -atmosphere -geosphere -biosphere -hydrosphere -sun

100000 years to now

The last 10,000 years are known as the Holocene. They have been uniquely stable and warm. Sea level stabilized at its current level about 7,000 years ago. This has allowed human civilization to develop. Even though temperatures were fairly stable compared to previous periods, there have still been slight climate variations in the recent climate history, such as a temperature decline between about 1600 and 1850, known as the Little Ice Age.

55 million years

The most recent transition between those phases occurred about 55 million years ago when the temperature reached a thermal maximum followed by a long period of cooling, which we are currently experiencing.

How is the climate changing there?

The permafrost is thawing The coastal sea ice is melting The sea level is rising Weather intensity is increasing All of these are happening at very high rates The temperature is increasing faster than any other regions (especially the Arctic) A nearly ice-free Arctic Ocean in September is likely before 2050

outgoing energy

half of solar radiation absorbed by the earth and atmosphere. the other half radiated back into the space is thermal energy

Tropical Storms

Tropical storms are known as typhoons, hurricanes and cyclones depending on where they happen in the world. In 2018, the number of tropical cyclones was above average in all four northern hemisphere basins. There were 74 northern hemisphere cyclones in 2018, well above the long-term average of 63. The north-east Pacific basin accumulated cyclone energy at its highest level since reliable satellite records began. The image below gives the rainfall estimate for Hurricane Florence for 18 September 2018 (Source: United States National Weather Service Eastern Region Headquarters).

Emission pathways

are modelled trajectories of global anthropogenic emissions over the 21st century. (Source: IPCC, 2018: Summary for Policymakers. In: Global Warming of 1.5°C. Glossary)

Infrared

conversion of energy into heat causes long wave radiation into the atmosphere

incoming energy

energy coming from the sun to the earth (solar radiation) and energy leaving the earth to outer space (energy balance)

solar radiation

radiant energy emitted by the sun from a nuclear fusion reaction that creates electromagnetic energy

No-climate-policy baseline

refers to the projected baseline emissions based on current policies presently in place around the world. (Sources: IPCC AR5 Working Group III and Climate ActionTracker)

absorbed energy

solar energy absorbed by the earth and warms it