Nine cities around the world have hosted concerts to raise awareness about global warming and environmental issues.
Saturday's event at London's Wembley Stadium was one of the main focal points, with Madonna, Genesis and the Red Hot Chili Peppers among the headliners.
Snoop Dogg performed at the Hamburg concert
Other concerts took place in Tokyo, Hamburg, Sydney, Johannesburg, Rio de Janeiro, Shanghai, Washington DC and New Jersey.
BBC correspondents around the world sent these reports on how the day progressed.
0330 BST - JAMIE COOMARASAMY, NEW JERSEY
Alec Baldwin is loving The Police. The camera here in New Jersey keeps showing him, bobbing around with a wreath around his neck.
Old man that I am, I'm wondering how many of the crowd were listening to music when Sting and co split up - let alone when the preceding artist, Roger Waters, was recording Dark Side of The Moon with Pink Floyd.
Sting, of course, has a pretty long track record of campaigning to saving the rain forest, so he's an appropriate singer to round it all off.
0050 BST - GARY DUFFY, RIO DE JANEIRO
Another crowd-pleasing performance from an American artist on Copacabana. This time it was Macy Gray.
She brought other political messages to the show - printed across her striking white dress. On the front was one word: Darfur.
She also led the crowd in singing: "All we are saying is give peace a chance."
The other big cheer of the night was when the crowd was told that the Christ Redeemer statue in Rio was one of the Seven New Wonders of the World.
0030 BST - JAMIE COOMARASAMY, NEW JERSEY
There's a lot of anger on stage - about the state of the environment and about the fact that this concert is being referred to as the New York, not the New Jersey one.
Actor Zach Braff - whose first film as director, Garden State, was named after the nickname for New Jersey - got perhaps the loudest response from a largely local crowd when he said he was sick and tired of the mix up.
Lest he be accused of being parochial, he quickly reminded the crowd that this was a global issue, before introducing Madonna's performance in London on a big screen.
0010 BST - PETER BILES, JOHANNESBURG
The Joburg Live Earth concert ended with a real crowd-pleaser - the British group UB40.
It was well after midnight local time before the musicians reached their finale. By then, the rather slow start to the evening had been long forgotten.
Overall, it's been the African musicians who have spoken most eloquently of the dangers of global warming to their continent.
Africa may contribute only a tiny percentage of the world's carbon emissions, but there's a lot at stake here, and this has been a much-needed wake-up call.
2230 BST - FIONA PRYOR, LONDON
After 10 hours, 21 acts and a crowd of 63,000, London's leg of Live Earth drew to a close with a tremendous performance by the Queen of pop herself, Madonna.
Just before she came on, the whole of Wembley Stadium was plunged into darkness so only the flashes of cameras could be seen, a sight that can only be described as breathtaking.
With the lights still, off the US star appeared on stage under a signal spotlight singing Hey You. Gradually as the arena lights went up a choir of school children were revealed standing behind her.
Not one person in my eye line was sitting as the star sang Ray of Light while playing the guitar and dancing, (is there anything this woman cannot do?).
The performance was energetic, engaging and by far the most entertaining of the day.
After weeks of relentless rain in July, the weather surprisingly held all day which only added to the amazing atmosphere in the arena.
But after a day of being urged to recycle, turn off lights and trade in our cars for bikes, the question that everybody is asking is will it make a difference? Only time will tell.
2230 BST - GARY DUFFY, RIO DE JANEIRO
Darkness has now fallen over Copacabana but Brazilians like a late party, and the Live Earth Show is heating up.
American rapper Pharrell Williams is one of the first to really engage the audience. He scored an early hit by addressing the crowd in Portuguese before telling his band '"we have got to get them closer".
The sea of people on Copacabana soon had their arms in the air and were joining in.
2200 BST - PETER BILES, JOHANNESBURG
We're approaching the high point of the evening. Joss Stone is performing, after an energetic performance from Angelique Kidjo from Benin.
Benin singer Angelique Kidjo was among the performers in Johannesburg
During the changeover, South African anti-poverty campaigner Kumi Naidoo was joined on stage by two Kenyan women, in traditional dress, one from the northern Turkana District and the other from the Masai region.
They highlighted the way in which global warming has changed the lives of pastoralists in Kenya.
"The struggle against poverty and the fight to reverse climate change are one and the same", said Naidoo. "They need to be given equal priority".
2125 BST - STEVE ROSENBERG, HAMBURG
My eardrums are ringing from several hours of super loud Live Earth music. But judging from the litter strewn across Hamburg's football stadium, the end is near.
On stage now is German star Juli. She's bouncing all over the place with some catchy numbers - and the crowd's jumping and waving, too. Super stuff!
She's now performing her big hit - The Perfect Wave - released just before the 2005 Tsunami. After the disaster in Asia, the song had to be withdrawn for a period, but now it's playing again in public.
I'm getting annoyed with all the cigarette smoke wafting over me in the stands. Unlike Britain, Germany's still a smokers' paradise and they're puffing away with pride.
Mind you, that level of pollution is nothing compared to the country's coal fired power stations which continue to pump greenhouse gases into the atmosphere.
Still, Germany's way ahead of Britain when it comes to renewable energy and recycling - so the Germans can teach us a thing or two about how to tackle global warming.
2100 BST - FIONA PRYOR, LONDON
For anyone who was starting to feel slightly fatigued from standing or sitting for seven hours, The Beastie Boys certainly breathed life back into them.
Dressed in suits with dark glasses, they ran around the stage and played hits such as Sabotage and Intergalactic.
Next up was the Pussycat Dolls who came out scantily clad in hot pants and short vest tops.
Their energetic dance routine, I am sure, was enough to make most people in the crowd vow to hit the gym first thing in the morning.
Both acts steered clear of mentioning the environment, a welcome relief after all the messages that had been beamed to the crowd throughout the course of the day.
2100 BST - PETER BILES, JOHANNESBURG
One of South Africa's national treasures, Vusi Mahlasela, has appeared to rapturous applause.
Sadly, a technical glitch with his guitar left him singing his opening song - When You Come Back - unaccompanied.
The guy seems ill-fated. Yesterday, his microphone failed when he spoke at a joint news conference in Joburg with the other Live Earth artists.
When he got into full swing tonight, Vusi Mahlasela was joined by Angelique Kidjo for a duet, and she'll be back on stage later.
The musical acts have been interspersed with messages about climate change, but the overwhelming sense is that most people are here primarily for the music.
2050 BST - JAMIE COOMARASAMY, NEW JERSEY
Outside, in the car park, there are quite a lot of four wheel drives and quite a few people who've been trying to convince me that the next car they buy will definitely be a hybrid.
Onstage, meanwhile, the Oscar night double act briefly reformed; Leonardo DiCaprio introducing the man behind it all, Al Gore, to the crowd. He only made a brief speech - but he's expected to be back with the reformed Police.
I managed a brief word with KT Tunstall when she came off stage. She was very excited to have inspired her first ever Mexican wave.
How do you keep the momentum going from an event like this, I asked her. Her reply - "Don't make rubbish music. If no one buys your records, no one's going to listen to what you have to say..."
2030 BST - GARY DUFFY, RIO DE JANEIRO
The sun is starting to fade over Copacabana as the action starts on stage in the last of the live earth concerts to begin.
One of the first on stage was the Brazilian TV presenter and singer Xuxa, an iconic figure for many in this country.
There was an enthusiastic reception for her and the crowds are starting to grow around the huge stage erected on Copacabana Beach.
For the moment though, it looks like attendance is well below the hopes of organisers, but with the concert just getting underway they will be hoping that big names like Lenny Kravitz will boost the numbers.
2000 BST - FIONA PRYOR, LONDON
Ricky Gervais bravely took to the stage for the first time since his embarrassing appearance at Diana's memorial concert last weekend where he was forced to fill time on stage for several minutes with no material ready while he waited for Elton John to come on stage.
He told the waiting crowd that Live Earth was already running late.
"So I'm going to be off this stage whether Elton John is ready or not," he joked.
The most entertaining part of the gig so far was from the spoof band Spinal Tap.
During one song other performers, including Paulo Nutini and James Blunt, appeared on stage playing bass for them.
Their set also included dwarves dressed as monks and falling rock props.
1900 BST - PETER BILES, JOHANNESBURG
The crowd is slowly growing in size, despite the cold on this winter evening that has clearly kept many South Africans at home.
"We're expecting 10,000 here tonight", says concert organiser John Langford.
"It's a bit chilly, and we've had a strange winter... is it climate change? We had snow in Joburg last week for the first time in 25 years."
Senegalese master musician Baaba Maal has got the audience moving with his fusion of traditional music with elements of pop and reggae.
Dr Amy Spriggs, an environmental expert, has just appeared on stage, posing a tough question for the residents of this city where so much is measured in terms of material wealth. "Do you really need to drive an SUV around Joburg?," she asked.
1900 BST - FIONA PRYOR, LONDON
"Today is the beginning of a very long journey," Keane frontman Tom Chaplin said.
"We can do something for the future of man kind and that's a beautiful thing."
He had the whole stadium singing along to their hit Somewhere Only we Know, telling the crowd he didn't "care if they don't know the words".
Walking out into the foyer it is clear to see today's message has already made an impact on some.
Recycle bins are overflowing with empty cartons and bottles. I saw several people weaving their way through the crowds with piles of empty food boxes heading to recycle them.
And I have been assured by a woman selling food on site that all burger boxes and bottles were made from recycled material.
1825 BST - STEVE ROSENBERG, HAMBURG
Things have turned nasty.
Up on stage, a stand-up comic from Bavaria has been insulting Hamburg and German northerners. I think he's missed the whole point. There are boos echoing round the football stadium. The guy's more unpopular than a carbon emission.
Good job Enrique Iglesias is taking over. Now the crowd's going wild. And the sun's come out too, so all the umbrellas have disappeared.
I've been chatting to fans in the crowd. It seems that Germans really have been changing their travel habits because of climate change.
Daniel told me he doesn't use a car - he reduces his carbon footprint by walking or taking the tram. And Anna says she decided not to buy a cheap air ticket to Milan out of concern for the environment.
1750 BST - FIONA PRYOR, LONDON
Nearly every performer has delivered their own message on the environmental crisis.
"You've got the world in your hands," Kasbian frontman Sergio Pizzorno told the cheering crowd.
The Black Eyed Peas gave an energetic performance encouraging the crowd to jump and down.
Spice Girl Geri Halliwell made a brief appearance on stage.
She admitted a combination of becoming a mother and the recent "freaky weather" has made her think about climate change.
"I really feel we have a responsibility to our children to take this seriously," she said.
The Red Hot Chili Peppers whipped the audience up into a frenzy as they played an extra long instrumental introduction to their hit Don't Stop, before lead singer Anthony Kiedis ran onto stage.
The arena erupted as he began singing and most people in the balconies leapt to their feet.
1735 BST - DAN GRIFFITHS, SHANGHAI
So that's it from Shanghai Live Earth.
The concert came to an end amid heavy rains and lightning. Hong Kong pop legend Eason Chan was the final act.
As the fans swarmed out of the stadium, I couldn't help but wonder about the impact on the country at large. China is one of the world's major emitters of greenhouse gases.
People here are aware of climate change but the simple fact is that most worry about getting a good job, a good home and a good car.
It's going to take a lot more than this concert in Shanghai to change that mindset.
1730 BST - PETER BILES, JOHANNESBURG
Live Earth Johannesburg opened with the Soweto Gospel Choir singing Homeless, a song made famous by Paul Simon's
1980s Gracelands album.
The Joburg concert is being staged at the Coca Cola Dome, an indoor stadium on the north-western outskirts of the city. The venue had to be moved from The Cradle of Humankind, a World Heritage site, because of logistical reasons.
There is a fairly small crowd here at this stage. The Joburg event has had little publicity, and climate change is not the issue of intense debate that it is in many developed countries.
But there is plenty of music to look forward to this evening. Joss Stone, Angelique Kidjo and UB40 will be on stage later.
1650 BST - JAMIE COOMARASAMY, NEW JERSEY
There's still an hour and a half until the Live part starts, but there's already plenty of Earth at the Giants stadium in New Jersey.
The area surrounding the concert venue is one huge building site; a vast wasteland, peppered with earth-moving equipment.
And while the local radio station, which is carrying the concert, claims that people have been talking about it for months, it's not until you get right up to the stadium that you see any advertising. It all feels rather last minute.
We were driven from the media car park to the stadium in a yellow school bus. Appropriately enough, I suppose, for an event that's as educational as it is musical...
1645 BST - STEVE ROSENBERG, HAMBURG
Big applause for Bianca Jagger.
She's chairperson of the World Future Council and appeared up on stage with a crowd of children from around the globe.
Here in Hamburg Bianca has launched a campaign to get kids to write letters to world leaders urging action on climate change.
Bianca Jagger was joined on stage by children bearing a message
The kids on stage sang a song, did some breakdancing and generally had a good time. But will those letters make presidents and prime ministers double their efforts to save the world?
Bianca Jagger told me later: "Children have the right to speak - we have failed children!"
She recalled that kids had written letters to Reagan and Gorbachev urging peace and look what happened: the Cold War came to an end.
No end in sight, though, to this concert.
1600 BST - FIONA PRYOR, LONDON
During a brief break between bands the crowd prove how much fun they are having by taking part in a huge Mexican wave which spread round the entire arena.
One could not help feeling sorry for actress Thandie Newton who appeared on stage to deliver her environmental message and to introduce Al Gore live from Washington.
However the Hollywood A-lister was left hideously high and dry on stage after being told in her ear-piece that Gore was not yet ready.
Thandie Newton resorted to talking about George Clooney
"I've always wanted to stand in front of 2 billion people with nothing entertaining or interesting to say," she joked before talking about the sexiness of George Clooney.
Desperation got the better of her though as she resorted to telling Wembley a knock knock joke (which I doubt will be included in the highlights of the event).
No one seemed to understand it, nevertheless the good natured crowd gave her a huge cheer anyway as she left the stage.
1500 BST - FIONA PRYOR, LONDON
So far so good - it is still hot and sunny in Wembley which is definitely helping to keep the smiles on everyone's faces.
One could not help feeling sorry for the Friday Night Project's Alan Carr who was used to fill in between bands.
The comic, clearly not used to using material about climate change in his routine, struggled to rouse much laughter.
A slow autocue did not help matters much as he delivered a few facts and figures about the dangers affecting the environment.
Razorlight managed to keep their set together despite "technical problems", but it was Snow Patrol that has really got the crowd going up until now.
The whole of Wembley erupted as the group played the opening chords to their hit single Chasing Cars (I doubt they considered the carbon emissions when they thought up the title of the song).
By the end of the song it seemed everyone in the balconies were on their feet singing along.
1435 BST - DAN GRIFFITHS, SHANGHAI
Torrential rain, fork lightning across the sky and thunder crashing in the distance. Welcome to Shanghai Live Earth!
The weather has really turned for the worst in the past hour or so. Some people are toughing it out, shivering under their umbrellas, but many have headed for the exits.
The gig in Shanghai is below the famous Oriental Pearl Tower
Those who have stayed are now listening to Sarah Brightman. She's pretty big in China and she's had an enthusiastic reception.
Half an hour to go to the end of the concert. Just wondering to myself, how many people are going to be left in the audience by then if the rain continues like this?!
1415 BST - STEVE ROSENBERG, HAMBURG
OK. So pop stars jet around the world leaving a big carbon footprint. But they do try to be green. Here in Hamburg, German star Mia told me she tries to use her rail card as much as possible.
US rapper Snoop Dog assured me he was very fond of wind power and solar energy (raising a few giggles from his entourage).
As for Roger Cicero (who represented Germany in this year's Eurovision Song Contest), well, he admitted he lets his girlfriend go round the house turning off all the lights that he's switched on.
1410 BST - NICK BRYANT, SYDNEY
Never before have I been at a rock concert where the final act was preceded by a map projected on to the big screens showing the nearest bus stops.
But never before have I been to a rock concert where a ride on public transport came included in the ticket price. It seemed to have the desired effect.
Normally, the parkland surrounding Aussie Stadium, and its more illustrious neighbour the Sydney Cricket Ground, is packed bumper to bumper with cars for sell-out occasions like this. Not today.
Sydney fans sang along as Crowded House played Weather with You
Travelling to the stadium by car was considered environmentally incorrect - even ordinarily, the SCG car parks have a nifty green-friendly pricing policy: you get a $A5 (£2.14) reduction for car-pooling.
So there wasn't the usual rush from the stadium before the event had ended.
Instead, most people stayed on to hear a much-anticipated performance from Crowded House, the newly-reformed band who played their farewell concert on the steps of the Sydney Opera House in 1996.
Led by a pumped-up Neil Finn, they were definitely worth the wait.
1405 BST - FIONA PRYOR, LONDON
The message about climate change did not deter touts from trying to flog tickets outside Wembley Stadium.
As I arrived I passed at least 20 people claiming they had "the best tickets around".
Genesis played hits including Invisible Touch at Wembley
Once seated, it is hard not to get caught up in the excitement of the moment, looking down on thousands of people in the magnificent, brand new Wembley Stadium.
Genesis were the first band to take to the stage in a blaze of sunshine (it has not gone unnoticed that the July sunshine has finally decided to make an appearance).
As the group started playing, thousands of arms shot up in the air to clap along.
Phil Collins greeted Wembley and said hello to the rest of the world after playing their opening song, Turn it on Again.
1400 BST - DAN GRIFFITHS, SHANGHAI
I spoke too soon in my last update. It has started raining here in Shanghai!
This is the organisers' worst nightmare because the concert is in an outdoor auditorium. But the band is playing on - or in this case, famous Chinese songstress Rong Zu Er.
Organisers are concerned about the weather, our correspondent says
It's only light rain at the moment so maybe things will get better.
The event has drawn crowds of passers-by who have come to see what's going on.
Construction workers on the building site opposite are looking down from their scaffolding in the sky. All around, the bright neon lights of Shanghai are lighting up the night.
1355 BST - STEVE ROSENBERG, HAMBURG
In Hamburg's biggest stadium, the nine-hour musical marathon has begun with Colombian singer-songwriter Shakira as the energetic curtain-raiser.
So far the bad weather's keeping the crowds away - the rain has been pouring down all day.
Shakira is among the acts on the bill in the German city of Hamburg
One fan I spoke to, Christian Peter, said he thought pop stars should walk, cycle or swim to concerts instead of taking the plane, to show they're serious about cutting CO2 emissions.
Well, on a rainy day like today, swimming to Live Earth is definitely an option.
1300 BST - GARY DUFFY, RIO DE JANEIRO
Rio de Janeiro feels like a "happening" kind of city this morning.
On one side of Copacabana the stage is set for Live Earth, and further down the beach there is last minute work going on for the Pan American Games, a major sporting tournament which starts here next week.
The stage for the Rio de Janeiro concert is right on the beach
There were not many signs that Live Earth had gripped the public imagination in the last few weeks, but it is a beautiful day in Rio, and that may well draw the crowds.
There was some uncertainty this week about whether this show could go ahead after a local prosecutor temporarily suspended the event, amid concerns the police here were overstretched.
But with that doubt removed, and the sun shining, Live Earth in Rio seems ready to go later on Saturday.
1230 BST - DAN GRIFFITHS, SHANGHAI
Shanghai Live Earth has begun!
Anthony Wong and Sarah Brightman are on the bill in Shanghai
It's amazing that it actually started at all.
The concert is in an open-air auditorium and there has been torrential rain all day.
It stopped just before proceedings started and the organisers are hoping that the rain will hold off for the next three hours.
Some of China's leading singers are on stage, but so far the audience of about 3,000 people has been pretty quiet.
These stars are going to have to work hard to get the crowd going.
0945 BST - CHRIS HOGG, TOKYO
I've just been having a chat to Phoenix from the US nu-metal band Linkin Park.
He was refreshingly honest about what can and can't be achieved here.
"Linkin Park is not trying to save the world," he told me. "But it's our goal to do what we can to clean up our world and make it a better place for our kids to live."
If that sounds too much like a glib soundbite for you, he pointed out that on their upcoming tour, they're putting in a series of measures such as switching to biofuels, which he says will save them the equivalent of driving 400,000 miles.
0850 BST - NICK BRYANT, SYDNEY
Now that Aussie Stadium has started to fill up, the event is becoming distinctly more, well, Aussie.
Despite the chill of the southern winter, there are long queues for recycled cardboard trays of ice-cold beer. Even an inflatable beach ball, that great staple of Australian sporting events, has bounced into view.
So, too, has a man who transcends the world of rock and green politics; whom his devotees claim stalks the corridors of power in Canberra, the capital, with the same self-assurance that he used to strut the stage.
The Sydney gig is at the Aussie Stadium, normally a sports ground
It's Peter Garrett, the dome-headed former lead singer of Midnight Oil and the Labor opposition's front bench spokesman on the environment.
Within minutes of the event starting off, there he was on the big screen, calling for citizens of the developed world to do more to combat global warming. And he'll be back later to personally introduce the headline act: Crowded House.
With a federal election looming later in the year, Garrett's mere presence gives this event a party political edge.
Al Gore, its organiser-in-chief, has already called John Howard and George W Bush - whose governments have refused to sign Kyoto - the "Bonnie and Clyde" of global warming.
0800 BST - CHRIS HOGG, TOKYO
The hall's really filling up now. We've had an hour or so of J-Pop, and from here on, the music gets a bit harder.
The most anticipated Japanese act is Kumi Koda who someone here described rather unfairly as like a Japanese Britney Spears. I'll let you know...
The organisers are claiming this gig will be carbon-neutral. Little details matter.
The green curry and rice I just ate came served in a cardboard bowl with a wooden spoon.
And I wasn't allowed to throw away my plastic water bottle until I'd removed the cap AND ripped the plastic label off.
0700 BST - CHRIS HOGG, TOKYO
Tokyo's Live Earth gig has kicked off at the massive Makuhari Messe stadium with a holographic message from Al Gore - popping up like Princess Leia at the start of Star Wars to appeal for help.
The venue is filling up steadily for this nine-hour gig. The fans streaming in passed nine different bins for them to sort their rubbish into.
We were asked to fill in a form detailing our carbon expenditure in getting here (luckily we came by train).
Trees will be planted in Indonesia to offset the carbon used.
The energy is coming from solar power. Food is organic.
The bands .. well the whole thing's kicking off with Japanese heavy rockers Rize, who are local favourites.
0400 BST - NICK BRYANT, SYDNEY
Live Earth was ushered in with the jolting sound of Australia's scorched red centre - the howl of a didgeridoo in a traditional Aboriginal welcome.
Then, in front of a sparse and still-gathering crowd, the band Blue King Brown took the stage, with black T-shirts emblazoned with the slogan "Say No to Nuclear Energy".
It's a contentious issue here, where the Howard government is looking into building nuclear power stations to meet the country's demand for energy.
Blue King Brown encouraged Sydney fans to reject nuclear energy
Next up, Toni Collette with her band The Finish, which includes her husband, Dave Galafassi.
The 34-year-old movie star, who shot to international fame in Muriel's Wedding, claims strong environmental credentials.
A conservation campaigner for the past decade, she drives a hybrid car, catches the ferry when she can and offsets her plane travel by investing in new energy initiatives.
As in the rest of the world, much of the pre-concert press attention in Australia has focused on the size and grubbiness of the carbon footprint of its globe-trotting stars.