# Global Climate Change: Impacts, Mitigation, and Adaptation Strategies

## Executive Summary

Climate change represents one of the most significant challenges facing humanity in the
21st century. Global average temperatures have risen by approximately 1.1°C above
pre-industrial levels, driven primarily by anthropogenic greenhouse gas emissions.
This report examines the current state of climate science, the observed and projected
impacts of climate change across key sectors, and evaluates mitigation and adaptation
strategies with emphasis on cost-effectiveness and scalability.

## 1. Observed Changes in the Climate System

### 1.1 Temperature Trends

Global surface temperature has increased faster since 1970 than in any other 50-year
period over at least the last 2,000 years. The five warmest years on record have all
occurred since 2015. Arctic warming has been particularly pronounced, with temperatures
rising at more than twice the global average rate — a phenomenon known as Arctic
amplification.

Ocean temperatures have also risen significantly. The upper 2,000 meters of the ocean
absorbed approximately 90% of the excess heat in the climate system. This oceanic
heat uptake has profound implications for marine ecosystems, sea level rise, and
weather patterns.

### 1.2 Cryosphere Changes

The Greenland and Antarctic ice sheets have been losing mass at an accelerating rate.
Between 2006 and 2018, the combined mass loss from both ice sheets averaged approximately
475 gigatons per year. Arctic sea ice extent has declined in every month of the year,
with September sea ice extent decreasing by approximately 13% per decade since 1979.

Mountain glaciers worldwide are retreating. This has significant implications for water
resources, as millions of people depend on glacial meltwater for drinking water,
agriculture, and hydroelectric power. In regions like the Hindu Kush-Himalayan range,
glacier retreat threatens water security for over 1.9 billion people.

### 1.3 Sea Level Rise

Global mean sea level rose by approximately 20 centimeters between 1901 and 2018.
The rate of rise has accelerated, from 1.3 mm/year during 1901-1971 to 3.7 mm/year
during 2006-2018. Projections indicate that by 2100, sea level could rise by 0.3-1.0
meters under moderate emissions scenarios, and potentially exceeding 2 meters under
high-emissions scenarios if ice sheet instabilities are triggered.

## 2. Impacts on Natural and Human Systems

### 2.1 Ecosystems and Biodiversity

Climate change is fundamentally altering ecosystems worldwide. Species are shifting
their geographic ranges poleward and to higher elevations at rates of approximately
17 km per decade for marine species and 11 km per decade for terrestrial species.
Coral reefs are particularly vulnerable — repeated mass bleaching events have
affected over 70% of the world's tropical reefs.

### 2.2 Food Security and Agriculture

Rising temperatures, changing precipitation patterns, and increased frequency of
extreme weather events are impacting agricultural productivity. Studies project
that global crop yields could decline by 2-6% per decade due to climate change,
while food demand is expected to increase by 50% by 2050. Tropical and subtropical
regions, where many developing countries are located, face the greatest risks.

### 2.3 Human Health

Climate change affects human health through multiple pathways: heat-related mortality,
expansion of vector-borne diseases (malaria, dengue), air quality degradation,
water-borne diseases, and mental health impacts. The WHO estimates that climate change
will cause approximately 250,000 additional deaths per year between 2030 and 2050.

## 3. Mitigation Strategies

### 3.1 Renewable Energy Transition

The cost of renewable energy has plummeted over the past decade. Solar photovoltaic
costs have decreased by 89% since 2010, while onshore wind costs have decreased by
70%. Renewable energy now accounts for the majority of new power capacity additions
globally. However, challenges remain in grid integration, energy storage, and ensuring
a just transition for fossil fuel-dependent communities.

### 3.2 Carbon Capture and Storage (CCS)

CCS technologies capture CO2 from point sources or directly from the atmosphere and
store it in geological formations. While technically feasible, deployment has been
slower than anticipated due to high costs and limited policy support. Direct Air
Capture (DAC) is particularly promising but currently costs $250-600 per ton of CO2.

### 3.3 Nature-Based Solutions

Forests, wetlands, and soils can sequester significant amounts of carbon. Reforestation
and afforestation could remove 3.6 gigatons of CO2 per year. Protecting existing forests
is equally important — tropical deforestation accounts for approximately 8-10% of
global greenhouse gas emissions. Regenerative agriculture practices can also enhance
soil carbon storage while improving food production.

## 4. Adaptation Strategies

### 4.1 Infrastructure Resilience

Building climate-resilient infrastructure requires incorporating future climate
projections into design standards. This includes designing drainage systems for
increased flood risk, elevating critical infrastructure above projected flood levels,
and using heat-resistant materials in construction.

### 4.2 Water Resource Management

Adaptive water management strategies include expanding water storage capacity,
improving irrigation efficiency, developing drought-resistant crop varieties,
and implementing water recycling and desalination technologies.

## 5. Conclusion

Limiting global warming to 1.5°C remains technically feasible but requires
unprecedented transformations in energy, land use, urban planning, and industrial
systems. The window for effective action is narrowing rapidly. Every fraction of
a degree of warming matters — the difference between 1.5°C and 2°C of warming
represents significantly greater risks to ecosystems, food security, and
human wellbeing.
