The climate of the world - a full summary

In the last 120 years, human impact on the world has been profound. Technological breakthroughs in communication, transportation, and medicine have transformed societies globally. Medical advancements, including antibiotics and genetic research, have markedly improved global health. However, this era has also brought environmental challenges due to industrialization, urbanization, and issues like climate change and pollution. Socially, strides have been made for civil rights, gender equality, and social justice. The interconnected globalized world has fueled economic growth but has also exposed disparities requiring collective solutions. Navigating present complexities necessitates addressing environmental sustainability, social equity, and ethical considerations for a positive future trajectory.

Is it the same planet

Today’s planet bears little resemblance to the one of 1850-1900. In the pre-industrial era, human activities had minimal impact on the climate. The IPCC assesses the impact of human-emitted greenhouse gases (GHG) on global warming and subsequent climate changes during this period.

IPCC Report Impact: The latest IPCC report paints a dire picture, suggesting that extreme weather events, seasonal changes, and rising sea levels are like a self-inflicted death sentence for humanity.
Code Red Warning: United Nations Secretary-General António Guterres describes the IPCC Working Group 1 Report as a “code red for humanity.”
Feedback Loop Mechanism: A warming atmosphere triggers fundamental changes in the planetary climate, resulting in shifts in climate zones and a lengthening of the growing season, particularly in the Northern Hemisphere extratropics.
Increased Rainfall: The warmer atmosphere’s enhanced moisture-carrying capacity leads to more frequent and intense rainy days. A 1°C temperature increase corresponds to a 7% intensification of rainfall.
Storm Track Changes: Storm systems have undergone alterations in their tracks, with mid-latitude storm tracks likely shifting poleward in both hemispheres since the 1980s, displaying marked seasonality in trends.
Human Influence: Human activities are linked to the poleward shift of the extra tropical jet in the Southern Hemisphere’s austral summer, contributing to changes in storm tracks.

The figures:

Global temperatures are on track to surpass 1.5°C in the next 20 years and hit 2°C by mid-century without substantial greenhouse gas emission reductions. Urgent global cuts are vital to curb future warming. Even achieving net-zero emissions by the mid-21st century may result in a slight 0.1°C overshoot of the 1.5°C limit. Failing significant emission reductions, the 2°C threshold is likely to be exceeded in the 21st century, according to the IPCC.

21st Century Warming: Average global surface temperature increased by 0.99°C compared to the 1850-1900 level in the first two decades. It rose 1.09°C above the historic base period in 2011-2020, signifying an accelerated planetary warming.
Historical Temperature: The current temperature is comparable to levels observed approximately 6,500 years ago during the Middle Holocene, which was warmer than the present day.
Post-AR5 Increase: Since the Assessment Report 5 (AR 5) in 2013, the estimated global surface temperature has risen, with +0.19°C attributed to further warming from 2003-2012.
IPCC Synthesis: Scientists in the IPCC report, synthesizing over 14,000 scientific reports, identify the principal factor in the increase in global surface temperature since AR5.
Near-Term Projections: Recent reports suggest the possibility of the world approaching the 1.5°C mark in the next five years for specific months or years, underlining the unprecedented warming caused by human activities.

Read Also: Climate Change

Prehistory:

The Earth hasn’t experienced comparable warming since 1,25,000 years ago, as revealed by palaeo-climate records spanning millions of years. Without significant greenhouse gas emission reductions, surpassing the 2.5°C mark above pre-industrial levels could result in a climate reminiscent of three million years ago, marked by distinct animal and plant species adaptations.

Melting it all away:

Global warming is causing the melting of the Earth’s Polar Regions, particularly evident in the Arctic. The annual average Arctic sea ice area hit its lowest point in 2011-2020 since at least 1850. Glacier retreat, a global phenomenon since the 1950s, is unparalleled in the last 2,000 years. A concerning prediction indicates that the Arctic might be devoid of sea ice in September at least once before 2050.

Warming and GHGs:

Global temperature rise aligns with increased greenhouse gas emissions. Since 2011, greenhouse gas concentrations, such as CO2, methane, and nitrous oxide, have surged, reaching levels unprecedented in the last two million years. In April 2021, CO2 concentration hit 416 parts per million, the highest in two million years. The undeniable increase in greenhouse gas concentrations since 1750 is unequivocally attributed to human activities.

Anthoropogenic for sure:

The report definitively links the increase in human-emitted greenhouse gases to the rise in global temperature, assigning a clear figure to the temperature rise caused by human-induced GHG emissions.

Human Responsibility:

Likely range of human-caused global temperature increase from 1850-1900 to 2010-2019: 0.8°C to 1.3°C.
Best estimate: 1.07°C.

Breakdown of Contributions:

Well-mixed GHGs: Contributed a warming of 1.0°C to 2.0°C.
Other human drivers (primarily aerosols): Contributed a cooling of 0.0°C to 0.8°C.
Natural drivers: Changed global surface temperature by -0.1°C to 0.1°C.
Internal variability: Changed it by -0.2°C to 0.2°C.

Summary:

To limit the temperature increase below 1.5°C, countries must adopt a low-emission scenario, necessitating a revision of their emission reduction targets as outlined in the 2015 Paris Agreement. The stark reality of climate change unfolds in the present, providing a glimpse of the challenges future generations will confront.

Read Also: Climate Terms Explained