As Greenland warms, its ice sheet may melt faster, and this surface warming may melt West Antarctica's ice sheet.

Paleoclimatic evidence suggests that an additional 2 °C (3.6 °F) of warming could destroy the Greenland Ice Sheet, raising the sea level by 5 to 6 meters (16 to 20 feet). -This would submerge many islands and lowlands.

The U.S. Gulf Coast and Eastern Seaboard (including the lower third of Florida), much of the Netherlands and Belgium (two European Low Countries), and heavily populated tropical areas like Bangladesh are vulnerable to sea level rise.

Tokyo, New York, Mumbai, Shanghai, and Dhaka are also in lowlands vulnerable to rising sea levels. Losing the West Antarctic ice sheet would raise sea levels by 10.5 meters (34 feet).

Current models predict that global sea level changes may take several centuries, but processes that accelerate ice sheet collapse may accelerate the rate.

Moulins—large, vertical shafts in the ice that allow surface meltwater to reach the base—are one such process.

The vast ice shelves off Antarctica support the continental ice sheet. If those ice shelves 

collapse, the continental ice sheet could become unstable, slide quickly toward the ocean, melt, and raise the mean sea level. Theoretical sea level rise models have not included either process.

Ocean circulation changes
Global warming may reduce the "thermohaline circulation" or "great ocean conveyor belt." 

Cold saline waters sink in the subpolar oceans, pushing warmer surface waters poleward from the subtropics.

-This process warms Iceland and coastal Europe, moderating their climates.

Some scientists believe global warming could shut down this current ocean system by releasing fresh water from melting ice sheets and glaciers into the subpolar North Atlantic Ocean.

Fresh water is less dense than saline water, so a significant intrusion would lower surface water density and inhibit the sinking motion that drives the large-scale thermohaline circulation.

Large-scale surface warming may cause colder conditions in North Atlantic regions. Modern climate model experiments suggest this is unlikely. 

Instead of cooling, a moderate thermohaline circulation weakening in the higher latitudes of the North Atlantic Ocean could dampen surface warming.

Tropical cyclone activity and global warming are controversial climate change topics. Global warming may increase tropical cyclone intensity and damage.

Rising ocean temperatures have been linked to stronger Atlantic hurricanes. Due to a lack of long-term measurements, tropical cyclone intensities in the tropical Pacific and 

Indian oceans are uncertain.

The number of tropical cyclones per year is unclear, but ocean warming increases tropical cyclone intensities. Wind shear may contribute.

Climate change may partially mitigate the effects of warmer temperatures by increasing wind shear in tropical cyclone-prone regions.

However, climate change's effects on ENSO make atmospheric wind changes uncertain.

Human-caused climate change is already causing hotter temperatures, rising sea levels, and stronger storms. 

Climate change's effects on mosquitoes carrying viruses or pathogenic bacteria on fruit are harder to see.

According to research, climate change increases the risk of zoonotic (animal-to-human) diseases. 

Dengue fever cases have increased as mosquitoes thrive in longer rainy seasons and more severe floods in Southeast Asia.

Lyme disease-carrying ticks are spreading across North America due to rising temperatures. They're also helping Central African bats and other Ebola suspects.

In South America, rainfall variability may increase rodent-borne hantavirus cases. Experts say climate-driven outbreaks are unprepared.

Developing countries will also suffer more from climate change. However, governments and international institutions can prevent the next global health emergency.

Dengue Fever in Southeast Asia

What is it?
Dengue is endemic in many tropical regions. It has been reported in 129 countries, and nearly four billion people—half the world's population—live in areas where the disease is a risk.

Asia accounts for 70% of the 100–400 million cases reported annually. Aedes aegypti mosquitoes spread dengue, and it rarely kills and usually causes fever and headache.

What’s the link to climate change?
Warm, wet conditions favour Aedes aegypti mosquitoes. As temperatures rise, insects can live in cooler areas. Warmer temperatures accelerate the development of disease-spreading mosquitoes.

As mosquitoes breed in standing water, floods can increase dengue cases. In 2021, Typhoon Rai hit the Philippines, increasing cases in several areas. Droughts cause people to store water in containers where mosquitoes lay their eggs.

How’s the threat changing?
If global temperatures rise, the U.N.'s Intergovernmental Panel on Climate Change warns that two billion more people could contract dengue. 

Due to longer rainy seasons, dengue fever outbreaks in Southeast Asia have skyrocketed. Dengue has also spread to non-endemic areas. 

As of August 2022, Brazil had nearly two million cases, the most in the world. Researchers warn that climate change could cause more dengue outbreaks in Japan, which had its first in 70 years in 2014.

How do countries manage it now?
Dengue-endemic countries control mosquitoes. Governments are using Wolbachia-carrying lab-bred male mosquitoes in addition to insecticides. These mosquitoes' eggs don't hatch. 

After a successful trial in Vietnam, several Southeast Asian countries are implementing D-MOSS, which analyzes satellite data and climate forecasts to predict dengue outbreaks seven months in advance. 

Public health departments also recommend mosquito nets, long-sleeved shirts and pants, and not keeping open water containers near the home. 

The first dengue vaccine was licensed in 2015, and the WHO recommends using it only as part of a prevention strategy. Despite its global threat, the disease is not addressed internationally.

Lyme Disease in North America

What is it?
Borrelia bacteria cause Lyme disease, which spreads across Asia, Europe, and North America. Black-legged ticks, which eat small mammals and birds, can infect humans. 

Lyme symptoms include fever, headache, fatigue, joint and muscle pain, and a bulls-eye skin rash. 

However, not everyone gets skin rash; it can take weeks for the body to produce enough antibodies to detect Lyme. 

Antibiotics treat most Lyme cases, but some patients have persistent symptoms for months or years.

What’s the link to climate change?
Warming spreads disease. Ticks thrive in temperatures above 45°F (7.2°C) and humid climates, so warming across North America provides better tick habitats. 

Like mosquitoes, a hotter climate speeds up a young tick's development into adulthood, shortening its reproductive cycle. 

Milder winters allow ticks to survive and stay active longer. Climate change also affects deer and other host populations.

How’s the threat changing?
Since the early 1990s, the number of new U.S. Lyme cases reported to the CDC has nearly doubled to around thirty thousand per year due to rising global temperatures. 

(The CDC notes that the actual caseload is likely higher, and U.S. insurance estimates put the number of Lyme diagnoses and treatments at around 475,000.) 

As greenhouse gas emissions rise, northeastern and upper midwestern U.S. states will significantly increase. Recently, Canada's caseload has increased from hundreds to thousands.

How do countries manage it now?
A 2015 study found that persistent Lyme symptoms cost the U.S. healthcare system $1.3 billion annually. Thus, the U.S. has heavily promoted Lyme prevention and early signs. 

Thousands of outdoor trails have CDC tick-prevention signs. Canada's public health agency has also promoted awareness, particularly among outdoor workers, and researchers are testing cheaper methods of public education.

Many scientists say they don't understand the disease, and research and development of new treatments have been underfunded.

Ebola in Central Africa

What is it?
Ebola is a relatively rare but severe infectious disease in Central Africa. The virus attacks the immune system, with typical symptoms including fever, vomiting, diarrhea, rash, and internal and external bleeding. 

Roughly half of all cases are fatal; of the forty-six known cases in 2021, there were twenty-seven deaths.

What’s the link to climate change?
Climate change should benefit disease-carrying animals. A warmer and wetter climate in DRC forests could produce more vegetation to feed more host animals. That increases virus transmission to humans. 

Ebola outbreaks have followed dry-to-wet seasons. Drought-prone areas may become food insecure. 

-This could drive them deeper into forested areas to find bushmeat (raw or minimally processed meat from animals like bats and monkeys) and other food, increasing their risk of contracting the virus.

How’s the threat changing?
Scientists say outbreaks have increased since the 1970s due to the region's growing population and urbanization. 

As temperatures rise and rainfall becomes more irregular, a 2019 British-U.S. study predicted that by 2070, the virus would spread to Africa several-fold. 

Given the difficulty of identifying the point of contact between an animal host and a person, scientific data on Ebola transmission to humans is limited.

How do countries manage it now?
Following a 2014–16 West African pandemic, the WHO and national governments overhauled crisis response. 

Since then, health experts have accelerated diagnostic tests, expanded therapeutic treatments, and developed new Ebola vaccines. 

Health agencies have also relied on local workers to build vaccine and response trust. Mistrust and disinformation continue to hinder these efforts, and African countries' tools are mostly for emergency response. 

Ebola vaccines only target specific strains and only close contact with patients. A vaccine-resistant Ebola strain caused a late 2022 outbreak in Uganda. The COVID-19 pandemic has further weakened regional health systems.

Hantavirus Diseases in South America

What is it?
Hantaviruses are a family of viruses typically spread by rodents. People can become infected through contact with aerosols from an infected rodent's saliva, urine or droppings. Hantavirus pulmonary syndrome is an often fatal respiratory disease, while those found in Asia and Europe can cause hemorrhagic fever with renal syndrome (HFRS).

What’s the link to climate change?
Several studies have linked environmental factors to hantavirus disease risk. Like Ebola, increased rainfall increases rodent populations and cases. Rodents seeking food in humans during droughts can also increase cases. 

Other studies suggest higher temperatures may increase cases. In São Paulo, Brazil, emissions-induced temperature rise could increase HPS risk by 30%.

How’s the threat changing?
Country-specific studies suggest climate change may increase global hantavirus cases. Though hantaviruses are unlikely to cause a pandemic, recent developments have raised concerns. 

Argentina and Chile's Andes hantavirus has spread more recently. HFRS symptoms usually appear two weeks after exposure, making the disease harder to track. As global 

temperatures rise, scientists want more research to predict outbreaks.

How do countries manage it now?
Few studies have examined whether an increase in hantavirus diseases worldwide is likely as a result of climate change, but evidence from individual countries suggests this may be the case. 

Current assessments by health officials place the risk of a hantavirus-caused pandemic at a low level, but recent events have raised some concerns. 

An increase in human-to-human transmission of the Andes hantavirus has been observed in recent years in those countries. 

The incubation period for HFRS is quite long, with symptoms not appearing for at least two weeks after exposure. 

Scientists have called for more research to identify potential hotspots as the global average temperature rises.

How Countries Can Prevent and Prepare
Worldwide, people will experience an increase in the frequency and severity of extreme weather events as the Earth continues to warm. 

Beyond these four diseases, hundreds more may see their threat level reduced. Baker, a professor at Brown University, says it's "hard to deny" that climate change is increasing the prevalence of infectious diseases. 

Yet, "the picture of how this looks in ten, twenty, thirty years is uncertain." Experts in public health and climate agree that governments must act quickly to close these entry points for disease and save lives. Some of the advice they give is as follows:

Increase research and surveillance.
Worldwide, people will experience an increase in the frequency and severity of extreme weather events as the Earth continues to warm. 

Beyond these four diseases, hundreds more may see their threat level reduced due to this. Baker, a professor at Brown University, says it's "hard to deny" that climate change is increasing the prevalence of infectious diseases. 

Yet, "the picture of how this looks in ten, twenty, thirty years is uncertain." Experts in public health and climate agree that governments must act quickly to close these entry points for disease and save lives. Some of the advice they give is as follows:

Develop vaccines and treatments.
Vaccines are the best pandemic prevention and control tools, but their development is complicated and expensive, and global production capacity is limited. Vaccine development accelerated during the COVID-19 pandemic. 

It highlighted vaccine inequity and debated patent waivers to increase vaccine access in low- and middle-income countries. 

Health experts recommend expanding vaccine research and development for expanding and emerging zoonotic diseases, especially universal vaccines that protect against all viruses in a family. 

A universal coronavirus vaccine would protect against COVID-19 and all animal-derived coronaviruses.

Public education and vaccination campaigns should be expanded to combat vaccine misinformation and scepticism, especially in historically marginalized communities.

Conclusion
Climate change is a global challenge affecting people in every country. It is already having profound impacts on all continents and across the oceans, with severe consequences for human security, economic development, and social welfare.